Invest Clin 66(2): 175 - 190, 2025 https://doi.org/10.54817/IC.v66n2a05

Corresponding author: Juan Cheng. Department of Gastrointestinal Surgery, Jiangsu Province (Suqian Hospital),

Suqian, 223800 Jiangsu, China. E-mail: syrchengj1984@163.com

Effects of oral nutritional supplementation

in a case-management model on body

composition changes in patients after

bariatric surgery.

Juan Cheng*and Yu Guo

Department of Gastrointestinal Surgery, Jiangsu Province (Suqian Hospital),

Suqian, Jiangsu, China.

Keywords: obesity; bariatric surgery; oral nutritional supplementation; case

management model; body composition; self-management.

Abstract. This study explores the effects of oral nutritional supplementa-

tion in a case-management model on body composition alterations in patients

after bariatric surgery. One hundred and twenty obese patients admitted to

the Jiangsu Province Suqian Hospital from January 2024 to March 2025 who

underwent bariatric surgery were included. Patients were divided into an obser-

vation group and a control group. The control group adopted routine nursing

measures. Based on routine nursing measures, the observation group adopted

an individualized nutritional supplement intervention according to the ideal

body weight and the principle of limiting energy intake. One and three months

after surgery, compared with the control group, the improvements of body fat

percentage, free fat mass (FFM), body mass index (BMI), body weight, skeletal

muscle mass, and excess weight loss rate in the observation group were more

significant. The albumin, hemoglobin, and total protein levels were higher;

emotional eating, external eating, restrained eating, and the Bariatric Surgery

Self-management Questionnaire (BSSQ) scores were significantly improved.

The scores of physical function, social function, physical pain, emotional func-

tion, general health, mental health, physical role, and vitality were higher. The

total incidence of postoperative complications was lower, while the total nurs-

ing satisfaction rate of patients was higher. To sum up, oral nutritional sup-

plementation in the case-management model can improve body composition,

promote nutritional status, reduce the incidence of complications, promote

postoperative self-management ability, and enhance the quality of life and nurs-

ing satisfaction in patients after bariatric surgery.

176 Cheng and Guo

Investigación Clínica 66(2): 2025

Efecto de la suplementación nutricional oral en un modelo

de cambios en la composición corporal en pacientes después

de cirugía bariátrica.

Invest Clin 2025; 66 (2): 175 – 190

Palabras clave: obesidad; cirugía bar iátrica; suplementación nutricional oral; modelo

de manejo de casos; composición corporal; autogestión.

Resumen. Este estudio tiene como objetivo explorar los efectos de la su-

plementación nutricional oral en un modelo de manejo de casos sobre las alte-

raciones de la composición corporal en pacientes después de cirugía bariátrica.

Se incluyeron 120 pacientes obesos ingresados en el Hospital de la provincia de

Jiangsu Suqian desde enero de 2024 hasta marzo de 2025 que se sometieron

a cirugía bariátrica. Los pacientes se dividieron en un grupo de observación y

un grupo control. Al grupo control se le aplicaron medidas de enfermería de

rutina. Con base a las medidas de rutina de enfermería, al grupo de observación

se le aplicó una intervención individualizada de suplementos nutricionales de

acuerdo con el peso corporal ideal combinado con el principio de limitar la

ingesta energética. Uno y tres meses después de la operación, en comparación

con el grupo control, las mejorías en porcentaje de grasa corporal, masa libre

de grasa, índice de masa corporal , peso corporal, masa muscular esquelética y

tasa de pérdida de exceso de peso en el grupo de observación fueron más signifi-

cativas. Los niveles de albúmina, hemoglobina y proteína total fueron mayores.

El dolor físico, la función emocional, el estado general de salud, la salud men-

tal, el papel físico y la vitalidad mejoraron; la incidencia total de complicacio-

nes postoperatorias, los puntajes del Cuestionario de Autogestión de la Cirugía

Bariátrica (BSSQ) y la tasa de satisfacción total de enfermería de los pacientes

fueron mayores. En resumen, la suplementación nutricional oral en el modelo

de manejo de casos puede mejorar la composición corporal, promover el estado

nutricional, reducir la incidencia de complicaciones, promover la capacidad

de automanejo postoperatoria, junto con una mejoría en la calidad de vida y la

satisfacción de la enfermería en pacientes de cirugía bariátrica.

Received: 01-02-2025 Accepted: 08-05-2025

INTRODUCTION

Obesity is recognized as a disease by the

World Health Organization, and according

to statistics, 38% of the global population

was overweight and obese in 2020, and this

figure is expected to rise to 51% by 2035 1.

According to the Dietary Guidelines for Chi-

nese Residents (2022), the number of obese

people in China ranks first in the world 2. At

present, the treatment of obesity is mainly

based on behavior, diet, exercise, drugs and

surgery 3. Compared with other treatments,

bariatric surgery can reduce weight more

quickly, effectively and sustainably in pa-

tients with morbid obesity or obesity compli-

cations by limiting food intake along with re-

ducing nutrient absorption, and has become

the most effective treatment for patients

with moderate and severe obesity 4. Studies

Oral nutrition is beneficial for patients after bariatric surgery 177

Vol. 66(2): 175 - 190, 2025

have shown that postoperative changes in

the digestive tract structure can affect nu-

trient absorption to varying degrees, thus

increasing the risk of malnutrition and asso-

ciated complications, and eventually leading

to malnutrition 5. Malnutrition is a common

clinical problem after bariatric surgery 6.

Therefore, nutrition management is essen-

tial for patients after bariatric surgery.

Body composition refers to the content

of various components in the body, contain-

ing three categories: fat mass, muscle mass

and bone mineral salt content 7. Muscle

mass’s physiological and metabolic function

differs from that of fat mass, and muscle mass

is the main metabolically active component

of the human body 8. Muscle mass loss may

affect the body mass loss rate after bariatric

surgery by reducing resting energy expendi-

ture 9. Loss of weight includes not only the

loss of fat mass, but also the loss of muscle

mass 10. Foreign studies have found that the

loss of muscle tissue after bariatric surgery

will have a negative impact on the long-term

effect of bariatric surgery, human health,

and quality of life, and can endanger the

life of patients in severe cases 11. The main

components of human muscle tissue include

lean body mass (LBM), fat-free mass (FFM),

along with skeletal muscle mass (SMM) 12.

The loss of FFM mainly occurs within three

months after bariatric surgery, when patients

are prone to malnutrition 13. At present, do-

mestic and foreign studies have shown that

in order to avoid the occurrence of postop-

erative malnutrition and reduce the loss of

FFM, patients are usually given at least 60

g/d of protein-rich low-carbohydrate oral nu-

tritional supplement after surgery, and whey

protein formula is the preferred formula 14.

However, most patients with bariatric sur-

gery have destructive eating behaviors be-

fore surgery, lack of health awareness and

poor self-control after surgery, and need dif-

ferent nutritional components and amounts

due to individual differences 15. Therefore,

individualized oral nutritional supplementa-

tion for patients after bariatric surgery may

effectively improve the clinical outcome of

patients, decrease the loss of muscle tissue

after bariatric surgery, improve the effect of

bariatric surgery along with improving pa-

tients’ dietary behavior compliance, so as to

better manage weight loss for patients 16.

Case management belongs to a health

care system for a disease that contains as-

sessment, planning, service, coordination,

and monitoring to meet the multiple health

requirements of individuals and promote

cost-effective and high-quality services 17.

The case-management model has been suc-

cessively applied to burns, acquired immune

deficiency syndrome, tuberculosis, cancer,

mental illness and other complicated dis-

eases, as well as chronic diseases such as

diabetes, hypertension and other long-term

care systems 18-20. In addition, the case man-

agement model has achieved specific results

in nutritional supplementation, emphasiz-

ing the importance of personalized man-

agement, and is currently used in all kinds

of population interventions with extensive

adaptability 21. However, case management

of oral nutritional supplementation in pa-

tients with bariatric surgery is rare.

Based on the case-management model,

this study constructed an oral nutritional

supplement program for patients after bar-

iatric surgery to explore the influence of this

program on the related indexes of body com-

position of patients after bariatric surgery,

in order to provide a theoretical basis and

practical guidance for nutritional manage-

ment of patients after bariatric surgery.

PATIENTS AND METHODS

General data

One hundred and twenty obese patients

admitted to our hospital from January 2024

to March 2025 who underwent bariatric sur-

gery were selected as study subjects. Inclu-

sion criteria: (1) Age ranged from 18-65 years

old; (2) In line with the surgical indications

of the “Expert Consensus on nutrition and

multidisciplinary management of bariatric

178 Cheng and Guo

Investigación Clínica 66(2): 2025

surgery”; (3) Patients undergoing their first

bariatric surgery; (4) Normal communica-

tion skills, skilled use of mobile APP’s. Exclu-

sion criteria: (1) Complicated with serious

heart, lung, kidney and other diseases; (2)

With mental illness; (3) Patients undergoing

corrective surgery; (4) Pregnant or lactating

women; (5) Incomplete clinical data collec-

tion. Patients were divided into an observa-

tion group and a control group following

the time order of operation, with 60 patients

in each group. No difference was seen in gen-

eral data between the two groups (p>0.05,

Table 1), reflecting comparability. This study

was approved by the ethical committee of

the Jiangsu Province Suqian Hospital and

followed the guidelines of the Declaration of

Helsinki of 1975, revised in 2013. Each pa-

tient has signed the informed consent.

METHODS

The control group adopted routine

nursing measures. Before bariatric surgery,

the routine preparation plan was conducted.

Postoperative education was guided accord-

ing to the phased diet principle: drinking

water (1-3 days after surgery) →blandliquid-

diet (1-2 weeks after surgery) → fluid diet

(3-4 weeks after surgery) → semi-fluid diet

(5-6 weeks after surgery) → soft food (7-12

weeks after surgery) → low-calorie balanced

diet (12 weeks after surgery). The daily wa-

ter intake was at least 1500-2000 mL, and

the patients were instructed to take special

vitamins for weight loss, orally, after surgery.

Patients began taking an oral protein pow-

der for weight loss on day 8 and consumed

at least 60 g of protein daily. The weight loss

education manual was distributed, and the

case manager was responsible for managing

the weight loss WeChat group and answer-

ing the patients’ questions. Patients were

urged to eat as required after discharge and

informed to go to the hospital for a follow-up

visit one and three months after surgery.

Based on routine nursing measures,

the observation group adopted an individu-

alized nutritional supplement intervention

according to the ideal body weight and the

principle of limiting energy intake.

(1) Setting up a research team. Nutri-

tion specialist nurse Juan Cheng and nu-

trition physician Liping Su developed an

individualized oral nutrition supplement

program for patients after bariatric surgery,

and chief physician Guodong Liu made ad-

justments. Yu Guo taught the patients to use

the “Menthol Health” nutritionist app and

record their dietary intake for 24 hours. The

nutrition specialist nurses analyzed and sort-

ed the collected data every week and dynam-

Table 1. General data of patients in the two groups.

Items Control group

(n=60)

Observation

group (n=60) t/χ2p

Gender Male 20 33.33) 18 (30.00) 0.154 0.694

Female 40 66.67) 42 (70.00)

Age (years) 31.26±4.21* 31.31±4.26 0.064 0.948

Marital status Married

Unmarried

39 65.00) 38 (63.33) 0.036 0.190

21 35.00) 22 (36.67)

Degree of education Junior high school

and below

10 (16.67)

11 (18.34)

0.068

0.966

Senior high school 24 (40.00) 23 (38.33)

University and above 26 (43.33) 26 (43.33)

Data is expressed as n (%); or *mean ± SD.

Oral nutrition is beneficial for patients after bariatric surgery 179

Vol. 66(2): 175 - 190, 2025

ically adjusted the intake plan of nutritional

preparations. Menglin Zhang was respon-

sible for the analysis and detection of body

composition one and three months after bar-

iatric surgery, and used the questionnaire to

issue the Dutch Eating Behavior Question-

naire (DEBQ) and the Bariatric Surgery

Self-management Questionnaire (BSSQ) to

understand the patients’ dietary compliance

and self-management ability. Lidan Zhao was

responsible for the statistics, and the statis-

tical data were entered and checked jointly

by the two of them. The statistician did not

participate in the design and implementa-

tion of the program.

(2) Oral nutritional supplement pro-

gram after bariatric surgery. On the day of

admission, the case manager measured the

patient’s height, weight, circumference and

body composition, conducted preoperative

diet education according to the measured

results, and established the case file. One

to two days after surgery, the nutrition spe-

cialist nurse instructed the patient to drink

a small amount of water several times, and

gave the patient warm water 20-30 mL/

time, 3-5 times, once/h, and instructed the

patient to drink slowly, 500 mL of water on

the day and 1000 mL of water on the second

day. Three to six days after surgery, the pa-

tient was given a bland liquid diet + whey

protein powder (45 g/d). The patient was

guided to drink 1500 mL of water, and the

patient’s energy intake was 600 kcal/d. One

to two weeks after surgery, the patient was

given a fluid diet + whey protein powder (60

g/d), and the patient’s energy intake was 10

kcal (kg·d). Three to four weeks after sur-

gery, the patient was given a semi-fluid diet

+ whey protein powder (60 g/d), and the

patient’s energy intake was 15 kcal (kg·d).

Two to three months after surgery, the pa-

tient was given soft food + whey protein

powder (60 g/d), and the patient’s energy

intake was 20 kcal (kg·d). Among them, the

dietary requirements for one week to three

months after surgery were 40% to 45% car-

bohydrates, 20% to 30% fat, 25% to 30% pro-

tein + weight loss special complex vitamins,

and daily drinking water ≥ 2000 mL.

Control Group: Postoperative diet

progression protocol

In this study, all patients followed a

structured diet advancement protocol after

bariatric surgery, beginning with clear fluids

and gradually progressing to a soft diet. The

dietary phases were as follows:

• Days 1–3 post-surgery: Clear fluids

only

• Weeks 1–2: Bland liquid diet

• Weeks 3–4: Full fluid diet

• Weeks 5–6: Semi-fluid/pureed diet

• Weeks 7–12: Soft food diet

• After week 12: Transition to a low-

calorie, balanced solid diet

This extended progression was based

on institutional protocol, aimed at reducing

the risk of early gastrointestinal intolerance

and complications. Protein supplementation

(minimum 60 g/day) was initiated during

the fluid phase and continued throughout

recovery. Patients were counselled to follow

prescribed meal volumes, texture guidelines,

and hydration targets (≥2000 mL/day).

All patients undergoing bariatric sur-

gery were provided with standardized pre-

operative dietary guidance upon admission

to the hospital. Specifically, patients were

instructed to follow a low-calorie, high-pro-

tein, low-carbohydrate liquid diet for seven

to ten days before surgery. This preoperative

diet was designed to reduce liver volume,

decrease visceral adiposity, and enhance

surgical visibility and safety. The prescribed

regimen typically included 800–1000 kcal/

day, with at least 60–80 g of protein, and

emphasized adequate fluid intake (≥1500

mL/day). Acceptable liquids included clear

broths, low-fat dairy, protein shakes, and

sugar-free beverages. Patients were advised

to avoid solid foods, sugary drinks, carbon-

ated beverages, and high-fat items. The case

180 Cheng and Guo

Investigación Clínica 66(2): 2025

management nurse conducted a brief in-hos-

pital orientation session to reinforce dietary

compliance, and adherence was monitored

through verbal recall and written logs dur-

ing preoperative assessments. Patients who

demonstrated non-adherence were coun-

selled and re-evaluated before surgical clear-

ance.

In the present study, the phrase “dy-

namically adjust the intake plan of nutrition-

al preparations” refers to the individualized

modification of oral nutritional supplement

(ONS) prescriptions based on the patients’

daily energy and protein intake, as recorded

through a dietary tracking app (Menthol Nu-

tritionist). These adjustments were not re-

lated to food preparation, culinary menu de-

sign, or traditional meal planning, but rather

to the quantitative regulation of supplement

dosage—particularly whey protein powder—

to ensure that nutritional intake aligned

with the patient’s postoperative recovery

phase and ideal body weight. Specifically,

adjustments targeted a protein intake of at

least 60 g/day and an energy intake ranging

from 10 to 20 kcal/kg/day, depending on

the time elapsed since surgery. The data col-

lected were reviewed weekly by the nutrition

specialist nurse and supervising nutrition

physician, who modified the amount and

timing of ONS accordingly. While this nurse-

led protocol provided a structured method

for managing macronutrient intake, we ac-

knowledge that it does not replace the com-

prehensive services of a registered dietitian

formally trained to develop evidence-based

individualized nutrition care plans. The ab-

sence of dietitian involvement represents a

limitation and underscores the need for fu-

ture studies to incorporate certified clinical

dietitians as core members of the bariatric

care team.

Observation indicators

(1) Patients were asked to weigh them-

selves on an empty stomach in the morning,

wearing light clothes and bare feet. The test

instrument was measured by an HCS-200RT

weight scale, with kg as the unit of mea-

surement, and the error was not more than

0.01 kg. A column height gauge measured

the height; the waist and hip circumference

were measured by a soft tape measure with

cm as the unit of measurement, and the er-

ror should not exceed 0.01 cm. The Inbody

3.0 body composition analyzer was used to

measure body composition. Body weight,

BMI, FFM, body fat percentage (%), skeletal

muscle mass and excess weight loss rate

were recorded after the test.

(2) Nutritional indicators, including

hemoglobin, albumin, and total protein,

were compared between the two groups.

(3) The total incidence of postoperative

complications, including abdominal hemor-

rhage, gastric fistula, vomiting, as well as

anastomotic stenosis, was compared be-

tween the two groups.

(4) DEBQ was used to assess the post-

operative eating behavior of patients in the

two groups 22. DEBQ included three dimen-

sions: emotional, external, and restrained

eating. 1 point represented “never,” and 5

points represented “always.” The higher the

score, the higher the level of corresponding

eating behavior.

(5) The Bariatric Surgery Self-Manage-

ment Questionnaire (BSSQ) is a validated

instrument designed to evaluate self-man-

agement behaviors critical to postoperative

recovery and long-term success following

bariatric surgery. The BSSQ consists of 33

items divided into multiple domains, in-

cluding:

1. Dietary behaviors (e.g., protein intake,

hydration, meal timing)

2. Physical activity adherence

3. Medication and supplement complian-

4. Self-monitoring behaviors (e.g., weight,

symptoms, food logs)

5. Emotional coping and support-seeking

behaviors

Oral nutrition is beneficial for patients after bariatric surgery 181

Vol. 66(2): 175 - 190, 2025

Each item is scored on a 5-point Likert

scale ranging from “Never” (1) to “Always”

(5), with higher scores indicating better ad-

herence to recommended self-management

practices. The total score ranges from 33

to 165, and in our study, it was rescaled

to a 0–99 scale for comparative purposes.

The BSSQ was administered postoperative-

ly to both groups at one and three months

by trained study personnel. Patients in the

observation group were counselled more

intensively on these domains as part of the

case-management model, which may have

contributed to their significantly higher

BSSQ scores.

(6) The quality of life was assessed using

the Short-Form 36 (SF-36) score 24, which in-

cluded eight dimensions (physical function,

social function, physical pain, emotional

function, general health, mental health, role

physical, and vitality), with a score of 0-100

for each dimension. The quality of life was

positively correlated with the score.

(7) During hospitalization, the nursing

satisfaction questionnaire made by our hos-

pital was used to evaluate nursing satisfac-

tion of patients, with a full score of 100. Ac-

cording to the score, it could be divided into

satisfaction (score ≥80 points), basic satis-

faction (60 points ≤ score <80 points) and

dissatisfaction (score <60 points). Nursing

satisfaction = (number of satisfaction cases

+ number of basic satisfaction cases)/total

cases ×100%.

Assessment of dietary and vitamin intake

compliance

Actual dietary intake—including pro-

tein, energy, fluid, and vitamin supplement

consumption—was monitored using the

Menthol Nutritionist app, where patients

in both groups were instructed to record

their 24-hour food and supplement intake.

Compliance was assessed weekly by the case

management team, with guidance provided

for underreporting or deviations from the in-

structed plan. However, quantitative intake

was only analyzed in the observation group,

where the app data were actively used to tai-

lor ONS dosages. In the control group, while

intake logs were encouraged and verbally

reviewed during follow-ups, no structured

method was used to quantify or verify adher-

ence to the prescribed dietary or vitamin

regimen. Laboratory markers such as hemo-

globin, albumin, and total protein were used

as indirect indicators of nutritional adequa-

cy, but specific micronutrient levels (e.g.,

iron, B12, vitamin D) were not assessed.

Micronutrient supplementation protocol

All patients were routinely prescribed a

standardized bariatric multivitamin complex

starting from the first week after surgery to

address the risk of postoperative micronutri-

ent deficiencies. The formulation used con-

tained at minimum:

• Iron (≥45 mg)

• Vitamin B12 (≥350–500 mcg)

• Folic acid (400–800 mcg)

• Calcium citrate (≥1200–1500 mg)

with Vitamin D3 (≥3000 IU)

• Vitamin A (≥5000 IU), Vitamin E,

and Zinc in bariatric-recommended do-

sages

This formulation followed the guide-

lines established for post-bariatric patients

to prevent common deficiencies in iron, B12,

folate, calcium, and fat-soluble vitamins. Pa-

tients were advised to take divided doses

(e.g., twice daily) and were monitored for

adherence during follow-up visits. The same

vitamin regimen was provided to the control

and observation groups to avoid bias intro-

duced by unequal micronutrient support.

Oral nutritional supplement program

after bariatric surgery

Personalization of ONS Based on Ideal

Body Weight and Energy Restriction in the

observation group, oral nutritional supple-

mentation (ONS) was tailored using a sim-

182 Cheng and Guo

Investigación Clínica 66(2): 2025

plified protocol based on each patient’s ideal

body weight (IBW) and postoperative energy

restriction targets. IBW was calculated using

the standard formula:

• IBW (kg) = 22 × height² (m²)

• Daily energy intake goals were set ac-

cording to the postoperative phase:

• Week 1–2: 10 kcal/kg IBW/day

• Week 3–4: 15 kcal/kg IBW/day

• Week 5–12: 20 kcal/kg IBW/day

Protein requirements were uniformly

set at a minimum of 60 g/day, adjusted up-

ward if tolerated, particularly for patients

with higher baseline BMI or physical activity

levels.

All patients in the observation group re-

ceived the same brand of whey protein pow-

der (a medical-grade, high-biological-value

supplement), but dosages were individual-

ized to help patients reach their energy and

protein targets when food intake was inad-

equate. The protein powder contained ap-

proximately 25 g of protein and 150 kcal

per serving, and was administered in divided

doses (1–3 servings/day) based on intake

gaps identified through dietary logs. No

flavor or formula variations were used, and

micronutrient content was not adjusted in-

dividually—this was standardized and sup-

plemented through bariatric multivitamin

capsules given to all patients.

Specification of whey protein supplement

used

All patients in the observation group re-

ceived the same commercially available whey

protein supplement, a whey protein isolate

powder containing approximately 25 g of

protein, 2 g of carbohydrates, 1 g of fat, and

150 kcal per 30 g serving. The supplement

was not fortified with vitamins or minerals,

and therefore did not serve as a complete

meal replacement. It was used exclusively to

meet daily protein intake targets (minimum

of 60 g/day) and routine bariatric multivi-

tamin supplementation. Patients consumed

1–3 servings daily based on their estimated

protein gap from dietary intake, calculated

using ideal body weight and reported food

logs.

Statistical analysis

SPSS 24.0 statistical software was ad-

opted for data analysis. Measurement data

were expressed as ±SD, and t-test and

ANOVA were adopted for comparison. Count

data were expressed as [n (%)], and the χ2

test was adopted for comparison. p<0.05

represented that the difference was statisti-

cally significant.

RESULTS

Body composition of patients in the two

groups

At one and three months after surgery,

the body fat percentage, FFM, BMI and body

weight in both groups were lower than base-

line (p<0.05), while the skeletal muscle

mass and excess weight loss rate in both

groups were higher than baseline (p<0.05).

Meanwhile, relative to the control group,

the improvements of the above body compo-

sition in the observation group were more

significant (p<0.05), as displayed in Fig. 1.

Nutritional status of patients in the two

groups

At 1 and 3 months after surgery, the

body fat percentage, albumin, hemoglobin

and total protein levels in both groups were

higher than baseline (p<0.05). Meanwhile,

relative to the control group, the levels of

albumin, hemoglobin, and total protein in

the observation group were higher (p<0.05,

Fig. 2).

Incidence of postoperative complications

in the two groups

Relative to the control group, the total

incidence of postoperative complications in

the observation group was lower (p<0.05,

Table 2).

Oral nutrition is beneficial for patients after bariatric surgery 183

Vol. 66(2): 175 - 190, 2025

Fig. 1. Body composition of patients in the two groups. #p<0.05, vs baseline (ANOVA); *p<0.05, vs control

group (t test).

Table 2. Incidence of postoperative complications in the two groups.

Groups N Abdominal

hemorrhage

Gastric

fistula

Vomiting Anastomotic

stenosis

Total incidence

rate

Control group 60 3 (5.00) 2 (3.33) 3 (5.00) 3 (5.00) 11 (18.33)

Observation group 60 0 (0.00) 1 (1.67) 1 (1.67) 1 (1.67) 3 (5.01)

χ25.175

p 0.022

Data is expressed as n (%).

Fig. 2. Nutritional status of patients in the two groups. #p<0.05, vs baseline (ANOVA); *p<0.05, vs control

group (t test).

184 Cheng and Guo

Investigación Clínica 66(2): 2025

Postoperative eating behavior of patients

in the two groups

At 1 and 3 months after surgery, the

scores of emotional eating and external eat-

ing in both groups were lower than baseline

(p<0.05), while the score of restrained eat-

ing in both groups was higher than baseline

(p<0.05). Meanwhile, relative to the con-

trol group, the improvements of the scores

of emotional eating, external eating and

restrained eating in the observation group

were more significant (p<0.05), as displayed

in Fig. 3.

Postoperative self-management behaviors

of patients in the two groups

At 1 and 3 months after surgery, the

BSSQ scores in both groups were higher

than baseline (p<0.05), and relative to the

control group, the BSSQ scores in the obser-

vation group were higher (p<0.05), as dis-

played in Fig. 4.

Quality of life in the two groups

At 1 and 3 months after surgery, the

scores of physical function, social function,

physical pain, emotional function, general

health, mental health, role physical, and vi-

tality in both groups were higher than base-

line (p<0.05). Relative to the control group,

the scores of physical function, social func-

tion, physical pain, emotional function, gen-

eral health, mental health, role physical, and

vitality in the observation group were higher

(p<0.05), as displayed in Fig. 5.

Nursing satisfaction of patients the two

groups

Relative to the control group, the total

nursing satisfaction rate of patients in the

observation group was higher (p<0.05, Ta-

ble 3).

DISCUSSION

Obesity is a pathological condition in

which fat accumulates excessively, usually

caused by excessive nutrient intake 25. Obe-

sity is linked to an increased risk of hyper-

tension, diabetes, lipid disorders, sleep dis-

orders, coronary heart disease, and stroke

26. Studies have shown that reducing weight

Fig. 3. Postoperative eating behavior of patients in the two groups. #p<0.05, vs baseline (ANOVA); *p<0.05,

vs control group (t test).

Fig. 4. Postoperative self-management behaviors of

patients in two groups. #p<0.05, vs baseline

(ANOVA); *p<0.05, vs control group (t test).

#p<0.05, vs baseline; *p<0.05, vs control

group.

Oral nutrition is beneficial for patients after bariatric surgery 185

Vol. 66(2): 175 - 190, 2025

and fat accumulation can significantly ex-

tend national life expectancy and reduce the

financial burden of health care 3. Current

approaches to weight loss include lifestyle

interventions, medication, and surgery 27.

Some weight-loss medications, particularly

older-generation agents, have been associ-

ated with neuropsychiatric side effects such

as anxiety, insomnia, or mood changes, but

these risks vary significantly depending on

the specific drug and patient profile. Newer

agents (e.g., GLP-1 receptor agonists) have

shown a favorable safety profile in clinical tri-

als, with few reports of severe mental health

effects 28-31. Protein isolates—particularly

whey protein isolate—are known to provide

highly bioavailable protein and have been

shown to support muscle mass retention

in postoperative patients. However, protein

supplements’ bioavailability and nutritional

value vary considerably depending on their

source, formulation, and protein concentra-

tion. For example, whey protein concentrates

typically contain less protein and more lac-

tose and fat than isolates, while protein wa-

ters may vary widely in their protein type and

quantity. Most standard protein supplements

also lack the comprehensive micronutrient

profile found in complete protein meal re-

placements designed for bariatric patients.

Therefore, accurate protein type and nutri-

ent content specification is essential when

interpreting their clinical impact.

However, after long-term practice, it

has been found that many patients have re-

duced self-control after surgery and find it

challenging to maintain good habits, which

seriously affects the therapeutic effect of

oral nutritional supplements 34. The case-

management model is a new nursing work

and service concept that extends and con-

tinues the current holistic nursing model 35.

Fig. 5. Quality of life in the two groups. #p<0.05, vs baseline (ANOVA); *p<0.05, vs control group (t test).

#p<0.05, vs baseline; *p<0.05, vs control group.

Table 3. Nursing satisfaction of patients in the two groups.

Groups N Satisfied Barely satisfied Dissatisfied Total satisfaction

Control group 60 30 (50.00) 20 (33.33) 10 (16.67) 50 (83.33)

Observation group 60 35 (58.34) 23 (38.33) 2 (3.33) 58 (96.67)

χ25.926

p 0.014

Data is expressed as n (%).

186 Cheng and Guo

Investigación Clínica 66(2): 2025

In the case-management model, the nurse

plays the role of the person in charge of case

management, is responsible for coordinat-

ing and communicating with doctors, medi-

cal teams and patients, formulating disease

treatment plans and objectives, adjusting

the plans based on the patient’s situation,

and constantly meeting the requirements of

patients, so that they can achieve expecta-

tions within the scheduled period and have

good clinical application effects 36.

Most anthropometric parameters, such

as waist circumference, hip circumference,

height, weight, and BMI, were used to assess

the weight loss effect of patients after bariat-

ric surgery. However, these indicators could

not accurately reflect the body fat percent-

age and muscle content of obese patients,

which had certain limitations 37. The Inter-

national Obesity Research Organization has

indicated that the use of various tools to as-

sess nutritional status, thereby improving

treatment and medical nutritional support,

is highly likely to decrease the morbidity bur-

den of obese patients, so a growing number

of studies have begun to focus on changes

in body composition of patients after bariat-

ric surgery 38. After this procedure, changes

in body composition, such as a sustained

reduction in fat mass, are often associated

with the inevitable loss of FFM 11. Excessive

loss of FFM is undesirable because FFM is re-

sponsible for most of the resting metabolic

rate, regulating core body temperature,

maintaining bone integrity, and maintain-

ing function and quality of life as the body

ages 39. In our study, the results indicated

that one and three months after surgery, the

improvements of body fat percentage, FFM,

BMI, body weight, skeletal muscle mass and

excess weight loss rate in the observation

group were more significant, suggesting that

oral nutritional supplementation in the case

management model could improve the body

composition of patients after bariatric sur-

gery. Consistently, Grupińska et al. suggest-

ed that oral nutritional supplements could

improve body composition in women with

breast cancer undergoing chemotherapy 40.

Moreover, our study also showed that at

one and three months after the operation,

relative to the control group, the improve-

ments of the scores of emotional eating, ex-

ternal eating and restrained eating, as well

as BSSQ scores in the observation group,

were more significant. Meanwhile, at one

and three months after the operation, rela-

tive to the control group, the scores of physi-

cal function, social function, physical pain,

emotional function, general health, mental

health, role physical, and vitality in the ob-

servation group were higher, suggesting that

oral nutritional supplementation in the case

management model could promote postop-

erative self-management ability, dietary com-

pliance and quality of life in patients after

bariatric surgery. In addition, we also found

that oral nutritional supplementation in the

case management model could enhance the

nursing satisfaction of patients after bariat-

ric surgery, which was in line with a study

proposed by Dong et al. 46. Although both

groups received the same standard bariatric

multivitamin complex, we acknowledge that

the effects of vitamin supplementation could

have interacted with or amplified the effects

of oral nutritional supplements (ONS), par-

ticularly on markers of nutritional status

such as hemoglobin, albumin, and protein

levels. Therefore, while efforts were made

to isolate the impact of ONS, micronutrient

correction via vitamin intake may have con-

tributed to improved outcomes, potentially

confounding the degree to which results can

be attributed to ONS alone. Future studies

may consider a factorial design or biochemi-

cal monitoring of micronutrient levels to

better disentangle these effects.

In conclusion, oral nutritional supple-

mentation in the case-management model

can improve body composition, promote nu-

tritional status, reduce the incidence of com-

plications, promote postoperative self-man-

agement ability, and enhance the quality of

Oral nutrition is beneficial for patients after bariatric surgery 187

Vol. 66(2): 175 - 190, 2025

life and nursing satisfaction in patients after

bariatric surgery.

Recommendation

Future studies and clinical programs

should prioritize the integration of regis-

tered clinical dietitians into case manage-

ment models for postoperative bariatric

patients. Including dietitians in multidisci-

plinary teams can ensure evidence-based,

individualized nutritional care, leading to

better outcomes in body composition, nutri-

tional status, complication rates, and patient

satisfaction. Institutional support to recruit

and embed clinical dietitians into surgical

and nutritional care pathways should be a

strategic priority to align with international

best practices.

Limitation

One notable limitation of our study is

the prolonged timeline of postoperative diet

advancement, with soft foods introduced

only after six weeks postoperatively, lasting

until week 12. This approach deviates from

widely accepted post-bariatric surgery pro-

tocols in other regions, where soft foods are

typically introduced by week 4, with transi-

tion to solid textures occurring by weeks

6–8. While our institution adopted a conser-

vative progression to minimize gastrointesti-

nal complications, this prolonged dietary re-

striction may have introduced confounding

variables. Without personalized nutritional

supplementation, patients in the control

group may have experienced greater caloric

deficits, reduced protein intake, and height-

ened dietary restraint—factors that could

influence body composition, nutritional

status, and psychological outcomes such as

restrained eating. These effects may have

amplified the observed benefits in the inter-

vention group. Future studies should consid-

er aligning with standard international diet

progression guidelines to ensure broader

generalizability and minimize the confound-

ing impact of diet texture timelines.

A significant limitation of this study

is the lack of objective, standardized

tracking of dietary and vitamin intake in

the control group. While the observation

group utilized a digital app for real-time

tracking and individualized ONS adjust-

ments, intake data from the control group

were based on self-reported logs and ver-

bal follow-ups, which may introduce re-

call bias or underreporting. Furthermore,

biochemical assessments of individual mi-

cronutrients were not conducted, limit-

ing our ability to distinguish the effects

of vitamin supplementation from the ONS

protocol. This discrepancy in intake moni-

toring between groups may affect the ac-

curacy of outcome comparisons.

ACKNOWLEDGMENTS

Thanks to Liping Su, Guodong Liu,

Menglin Zhang and Lidan Zhao for their in-

valuable assistance.

Funding

This work received no funding.

Declaration of competing interest

The authors declare that they have no

conflicts of interest.

Number ORCID of authors

• Juan Cheng: 0009-0008-3989-8416

• Yu Guo: 0009-0005-1230-5682

Credit authorship contribution statement

JC designed the study, collected data,

and drafted the manuscript. YG performed

data analysis, revised the manuscript, and

drew figures.

188 Cheng and Guo

Investigación Clínica 66(2): 2025

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