In this study, 252 students who were willing to participate were recruited in the form of posters, leaflets, and radio broadcasts to publicize the project at a university in Luoyang City in October 2023, and they were analyzed for body composition. Inclusion criteria: 1) body fat percentage > 20% for males and >28% for females (as determined by the instruction manual of the Inbody-260, the body composition analyzer used in this experiment); 2) not having been on a restrictive diet in the 6 months prior to the start of the study. Exclusion criteria: 1) diagnosis of diabetes mellitus, prior ischemic heart disease, cerebrovascular disease, or severe mental illness; 2) physical impairment that prevents participation in physical activity; 3) receipt of any weight-loss treatment elsewhere; and 4) inaccessibility to the Internet. The study was approved by the Ethics Committee of the 989th Hospital of the Joint Logistics Department of the Chinese People’s Liberation Army, and all methods were performed in accordance with relevant guidelines and regulations. All participants signed an informed consent form.

Internet-based diet, exercise, and combined intervention for overweight and obese college students; pre-intervention body fat is 27.3 kg; hope that after the intervention, the average reduction is 0.7 kg; the standard deviation of the estimated difference is 1.2 kg; take α = 0.05 (two-sided), power = 90%, two-sided test, according to the formula for calculating the sample size:

$n=\frac{{\left(z_{\alpha }+z_{\beta }\right)}^2\ast {\sigma }^2}{{\delta }^2}$

can be obtained as n = 31 cases, because of its own matched-pair design, so there is no need to. The sample size was doubled, taking into account 10% lost visits as well as refusals, totaling at least 34 study cases, which were included.

The recruited subjects were divided into four groups according to the simple randomized grouping method: control group, dietary intervention group, exercise intervention group, and diet-combined exercise intervention group, with 35 subjects in each group.

All study subjects underwent anthropometric compositional measurements prior to the intervention, which were performed using an Inbody-260 body composition analyzer. Subjects fasted for at least 2 h before the test, emptied their bowels, wore light clothing and were prohibited from strenuous activities. During the body composition measurement, the subject stood barefoot on the footplate electrode and held the hand electrode with both hands. The measurer first recorded the subject’s basic personal information, such as age and gender, and then carried out the measurement, and the system automatically generated various body composition parameters of the subject. After the measurement was completed, there was an exchange with a nutritionist, who popularized nutritional knowledge and weight reduction methods to the subject, and formulated individualized diet and exercise recommendations for him/her based on the results of the body composition analysis.

1) Dietary regimen: Adopt the energy-limited balanced diet method, individualize the calculation of one day’s energy demand, and, on the basis of this energy, reduce the total energy intake by 500 - 1000 kcal or by 30% per day.

2) Exercise program: 150 - 300 minutes of moderate-intensity aerobic exercise per week, 5 - 7 days per week, at least once every other day; resistance exercise 2 - 3 days per week, once every other day, 10 - 20 minutes each time. Energy consumption through exercise is 2000 kcal or more per week.

3) Management team: Clinical dietitians, rehabilitators, and counselors with more than 5 years of clinical experience work together to develop individualized diet and exercise plans for students, answer questions, and provide psychological guidance.

4) Follow-up program: Four WeChat group chats were established after random grouping. Subjects independently carried out weight management according to the individualized diet and exercise recommendations and clocked in daily in the WeChat group. The researchers answered the subjects’ questions about weight management in the group at any time, and the intervention time was 6 weeks.

The study was statistically processed using SAS 9.1 and SPSS 21.0 statistical software, with normally distributed measures expressed as mean ± standard deviation ( $\bar{x}\pm s$), non-normally distributed measures expressed as median (interquartile spacing), and counts expressed as number of cases (percentage) [n (%)]. Differences in baseline characteristics between groups were analyzed using ANOVA or chi-square tests. When evaluating the effect of intervention, data that did not conform to a normal distribution were log-transformed to make them normally or approximately normally distributed; a paired t-test was used to compare the amount of within-group changes in each index before and after intervention; a multiple linear regression model was used to further explore the relevant factors affecting the changes in body fat percentage and to draw forest plots. All of the above tests were two-sided, and the test level was α = 0.05.

There were a total of 134 people in this study, including 35 in the control group (26.12%), 32 in the combined intervention group (23.88%), 34 in the dietary intervention group (25.37%), and 33 in the exercise intervention group (24.63%) according to the intervention modality. The differences in age, height, weight, and gender among the 4 groups were not statistically significant (P > 0.05). See Table 1 .

F: ANOVA; χ²: Chi-square test. SD: standard deviation.

Paired t-tests revealed significant within-group changes in body composition indicators following the 12-week intervention period, as detailed in Table 2 .

Body Mass Index (BMI): All intervention groups demonstrated significant reductions in BMI (all P < 0.001). The Joint Intervention Group exhibited the largest decrease (Mean Difference [MD] = 1.000 kg/m², 95% CI: 0.656 to 1.344, t = 5.927), followed by the Dietary Intervention Group (MD = 0.403 kg/m², 95% CI: 0.239 to 0.567, t = 4.999) and the Exercise Intervention Group (MD = 0.391 kg/m², 95% CI: 0.210 to 0.572, t = 4.402). In contrast, the Control Group experienced a small but statistically significant increase in BMI (MD = −0.191 kg/m², 95% CI: −0.304 to −0.079, t = −3.467, P = 0.001). Body Fat Mass (kg): Significant reductions in body fat mass were observed in the Joint Intervention Group (MD = 2.806 kg, 95% CI: 1.736 to 3.876, t = 5.348, P < 0.001), the Dietary Intervention Group (MD = 1.050 kg, 95% CI: 0.661 to 1.439, t = 5.488, P < 0.001), and the Exercise Intervention Group (MD = 0.785 kg, 95% CI: 0.240 to 1.330, t = 2.933, P = 0.006). The reduction was largest in the Joint Intervention Group. No significant change occurred in the Control Group (MD = −0.077 kg, 95% CI: −0.384 to 0.229, t = −0.511, P = 0.612). Body Fat Rate (BFR %): Both the Joint Intervention Group (MD = 2.419%, 95% CI: 1.394 to 3.444, t = 4.812, P < 0.001) and the Dietary Intervention Group (MD = 1.153%, 95% CI: 0.585 to 1.721, t = 4.127, P < 0.001) showed significant reductions in body fat percentage. The reduction in the Exercise Intervention Group approached but did not reach statistical significance (MD = 0.536%, 95% CI: 0.095 to 1.168, t = 1.731, P = 0.093). The Control Group showed no significant change (MD = 0.086%, 95% CI: −0.338 to 0.509, t = 0.411, P = 0.683). Waist-to-Height Ratio (WHR): Changes in WHR varied significantly between groups. The Joint Intervention Group showed a significant improvement (decrease) in WHR (MD = 0.029, 95% CI: 0.013 to 0.046, t = 3.554, P = 0.001). Conversely, the Control Group showed a significant increase (worsening) in WHR (MD = −0.012, 95% CI: −0.018 to −0.006, t = −3.785, P < 0.001). Neither the Dietary Intervention Group (MD = −0.007, 95% CI: −0.016 to 0.002, t = −1.566, P = 0.127) nor the Exercise Intervention Group (MD = −0.005, 95% CI: −0.015 to 0.004, t = −1.118, P = 0.272) exhibited significant changes in WHR. Skeletal Muscle Mass (kg): No significant increases in skeletal muscle mass were found in any intervention group (Joint: MD = −0.300 kg, P = 0.086; Dietary: MD = −0.041 kg, P = 0.763; Exercise: MD = 0.042 kg, P = 0.775). The Control Group exhibited a small but statistically significant decrease (MD = −0.191 kg, 95% CI: −0.372 to −0.011, t = −2.153, P = 0.039).

Intergroup analyses of change scores (post-intervention minus baseline) revealed significant differences between the intervention groups across multiple body composition indicators ( Table 3 ).

BMI Change: The Joint Intervention Group demonstrated significantly greater BMI reductions than all other groups: Control Group (P < 0.001), Dietary Intervention Group (P < 0.001), and Exercise Intervention Group (P < 0.001). While the Dietary and Exercise Intervention Groups both showed significantly greater reductions than the Control Group (both P < 0.001), their effects did not differ significantly from each other (P = 0.935). Body Fat Mass Change: The Joint Intervention Group achieved significantly larger body fat reductions than the Control Group (P < 0.001), Dietary Intervention Group (P < 0.001), and Exercise Intervention Group (P < 0.001). Both the Dietary (P = 0.010) and Exercise (P = 0.049) Intervention Groups showed significantly greater fat loss than the Control Group. No significant difference existed between the Dietary and Exercise Groups (P = 0.546). Body Fat Rate (BFR) Change: The Joint Intervention Group produced significantly greater BFR reductions than the Control Group (P < 0.001), Dietary Intervention Group (P = 0.009), and Exercise Intervention Group (P < 0.001). The Dietary Intervention Group showed significantly greater BFR reduction than the Control Group (P = 0.024), while the Exercise Group did not (P = 0.341). The difference between the Dietary and Exercise Groups was non-significant (P = 0.197). Waist-to-Height Ratio (WHR) Change: The Joint Intervention Group exhibited significantly greater WHR improvements (reductions) than the Control Group (P < 0.001), Dietary Intervention Group (P < 0.001), and Exercise Intervention Group (P < 0.001). Neither the Dietary (P = 0.481) nor the Exercise (P = 0.361) Intervention Group differed significantly from the Control Group. No difference existed between the Dietary and Exercise Groups (P = 0.830). Skeletal Muscle Mass Change: No significant differences in skeletal muscle mass changes were detected between any pair of groups (all P > 0.05).

Linear regression analyses identified significant predictors of changes in body fat percentage (BFR) following the intervention ( Table 4 , Figure 1 and Figure 2 ).

Significant predictors of greater BFR reduction included: Intervention groups (vs. Control): Joint Intervention (β = −2.33%, 95% CI: −3.26 to −1.40, P < 0.001), Dietary Intervention (β = −1.07%, 95% CI: −1.98 to −0.15, P = 0.024). Sex: Females showed greater reduction than males (β = −0.46%, 95% CI: −0.78 to −0.14, P = 0.006). Baseline adiposity: Higher baseline weight (β = −0.03%/kg, 95% CI: −0.05 to −0.01, P = 0.035), Higher baseline BMI (β = −0.10%/kg/m², 95% CI: −0.19 to −0.01, P = 0.028), Higher baseline body fat (β = −0.08%/kg, 95% CI: −0.12 to −0.03, P = 0.003), Higher baseline WHR (β = −15.13%/unit, 95% CI: −22.34 to −7.92, P < 0.001). Age, height, and baseline skeletal muscle mass were non-significant predictors.

After adjustment for covariates, independent predictors of BFR were: Intervention effects (vs. Control): Joint Intervention: β = −2.18% (95% CI: −3.06 to −1.30, P < 0.001). Dietary Intervention: β = −1.13% (95% CI: −2.00 to −0.26, P = 0.012). Exercise Intervention: Non-significant (β = −0.45%, 95% CI: −1.32 to 0.42, P = 0.317). Sex: Females achieved greater reductions (β = −0.33%, 95% CI: −0.63 to −0.02, P = 0.039). Baseline adiposity: Higher baseline body fat (β = −0.13%/kg, 95% CI: −0.26 to −0.01, P = 0.040). Higher baseline WHR (β = −12.82%/unit, 95% CI: −23.26 to −2.37, P = 0.018). Baseline weight and BMI became non-significant in the adjusted model.