Human Feeding Trial for Weight-Loss Function: Protocol, Testing Items, and Evaluation Criteria

A human feeding trial for weight-loss function is a controlled clinical intervention study designed to substantiate slimming and body-fat-control claims for health foods and functional food products. Conducted as a randomized, double-blind, placebo-controlled study, the trial objectively measures changes in body weight, body fat percentage, and waist circumference in overweight volunteers while confirming product safety. This article explains the study design, sample requirements, testing items, methods, judgment criteria, and regulatory applications of the weight-loss human feeding trial.

Technical Overview

A human feeding trial for weight-loss function is a standardized human intervention study used to evaluate whether a health food or functional food product can safely and effectively reduce body weight and body fat in human subjects. The study follows the principles of randomized, double-blind, placebo-controlled, parallel-group clinical research and is the key scientific evidence required when a weight-loss or fat-control function claim is declared in a product registration dossier.

Under the Chinese regulatory framework, the evaluation protocol was originally defined in the Technical Standards for Testing and Assessment of Health Food (2003 Edition) and has been updated in the Health Food Function Testing and Evaluation Methods (2023 Edition), in which the historical weight-loss function is re-designated as helping to control body fat. The trial typically enrolls at least 50 volunteers per group for an intervention period of no fewer than 35 days, during which body weight, body mass index (BMI), total fat mass, body fat percentage, and waist circumference are monitored alongside a full panel of safety indicators. All laboratory analyses are performed by accredited third-party laboratories operating in conformity with ISO/IEC 17025, and the clinical phase is conducted in qualified medical institutions in accordance with the Declaration of Helsinki.

Standards and Regulatory Framework

The design, execution, and judgment of the weight-loss human feeding trial are governed by a combination of national standards and ethical principles, including:

• Technical Standards for Testing and Assessment of Health Food (2003 Edition), which defines the classic human feeding trial protocol for the weight-loss function.
• Health Food Function Testing and Evaluation Methods (2023 Edition), which specifies current requirements for the body-fat-control function claim, including combined animal testing and human trial evidence.
• GB 16740, the national food safety standard for health food, covering hygiene and general safety requirements for the test product.
• WS/T 428, the health industry standard for the determination of adult weight status, used to classify overweight and obese subjects during screening.
• GB 15193 series, the national food safety standard for toxicological assessment, which must be completed before any human exposure.
• ISO/IEC 17025 requirements for the competence of testing and calibration laboratories performing the analytical work.
• The Declaration of Helsinki and national clinical research ethics regulations, requiring ethics committee approval and written informed consent from every participant.

Testing Samples

Eligible Sample Forms

The trial applies to finished health food products in any conventional oral dosage form intended for daily consumption, typically including:

• Hard capsules, soft capsules, and tablets
• Granules, powders, and effervescent formulations
• Oral liquids and functional beverages
• Functional teas, herbal infusions, and instant coffee preparations
• Meal-replacement powders, shakes, and nutrition bars

Sample and Placebo Requirements

Before the clinical phase begins, the test article must be supported by a complete set of pre-trial documentation and quality verification:

• Finished-product test reports covering physicochemical parameters and microbiological safety in accordance with applicable GB standards.
• Completed toxicological assessment reports, including acute toxicity and genotoxicity screening as required by the GB 15193 series.
• Stability data supporting integrity of the product throughout the intervention period.
• A placebo identical to the test article in appearance, packaging, color, flavor, and texture, differing only in the absence of functional ingredients.
• Randomization codes and blinding arrangements prepared by a party independent of the clinical investigators, with retention samples archived for verification.
• A human recommended daily intake derived from the animal studies and no-observed-adverse-effect-level data.

Testing Items

Testing items are divided into functional efficacy indicators, safety observation indicators, and dietary and lifestyle control indicators. Together they demonstrate both the weight-reducing effect of the sample and its safety for human consumption.

Functional Efficacy Indicators

• Body weight, measured under standardized conditions with a calibrated scale
• Body mass index (BMI), calculated from height and weight
• Total fat mass and body fat percentage, measured by bioelectrical impedance analysis or dual-energy X-ray absorptiometry
• Lean body mass and total body water, to confirm that fat loss does not come at the expense of muscle or body protein
• Waist circumference, hip circumference, and waist-to-hip ratio
• Skinfold thickness at the triceps, subscapular, and abdominal sites

Safety Observation Indicators

• Vital signs, including blood pressure and resting heart rate
• Electrocardiogram (ECG) examination before and after the intervention
• Hematology: white blood cell count, red blood cell count, hemoglobin, and platelet count
• Urine routine and stool routine examinations
• Serum biochemistry: alanine aminotransferase, aspartate aminotransferase, total protein, albumin, urea, creatinine, uric acid, fasting blood glucose, and lipid profile including total cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol
• Chest X-ray and abdominal ultrasound examinations at baseline
• Systematic recording of all adverse events and unexpected symptoms throughout the study

Dietary and Lifestyle Control Indicators

• Three-day dietary records and 24-hour dietary recalls to quantify energy and macronutrient intake
• Physical activity logs to ensure comparability of exercise levels between groups
• Menstrual history records for female subjects
• Compliance verification based on returned unit counts and interview confirmation

Testing Methods

Study Design

The trial is conducted as a randomized, double-blind, placebo-controlled, parallel-group study. Eligible subjects are randomly assigned in equal numbers to the test group and the placebo control group, with no fewer than 50 subjects per group. After a run-in period during which baseline stability is confirmed, subjects consume the test article or placebo at the recommended daily intake for an intervention period of at least 35 days while maintaining their habitual diet and physical activity under standardized guidance.

Subject Selection

Inclusion criteria typically require:

• Adults between 18 and 65 years of age
• Body mass index meeting the criteria for overweight or simple obesity as classified under WS/T 428, generally BMI of 24 or above
• Stable body weight in the months preceding enrollment
• Written informed consent and willingness to comply with the protocol

Exclusion criteria generally cover:

• Pregnant or lactating women and women planning pregnancy
• Individuals with cardiovascular, hepatic, renal, endocrine, or metabolic diseases, including diabetes and thyroid dysfunction
• Subjects currently taking weight-loss drugs or other weight-control functional products
• Individuals with known allergy to any ingredient of the test article
• Participation in another clinical trial within the preceding months
• Heavy smokers, alcohol abusers, competitive athletes, or individuals with eating disorders

Intervention and Observation Procedure

All anthropometric and body-composition measurements are performed at baseline and at the end of the intervention using the same calibrated instruments and standardized operating procedures, with subjects fasting and lightly dressed. Blood and urine samples are collected after an overnight fast for the full safety panel. Follow-up visits are scheduled weekly to record compliance, adverse events, dietary intake, and body weight. Quality control measures include technician training, instrument calibration records, duplicate measurements, and source-data verification by independent monitors.

Statistical Analysis

Within-group differences between baseline and endpoint values are analyzed using paired t-tests or non-parametric equivalents, while between-group differences are assessed using independent-sample t-tests. Categorical data such as individual response rates are compared using chi-square tests. A probability value of less than 0.05 is considered statistically significant, and analyses are performed on both per-protocol and full-analysis populations.

Judgment Criteria

A positive result for the weight-loss or body-fat-control function is supported when all of the following conditions are met:

• The test group shows statistically significant reductions in body weight, total fat mass, and body fat percentage compared with its own baseline values.
• The reductions in body weight, total fat mass, and body fat percentage in the test group are significantly greater than those in the placebo group.
• Lean body mass shows no statistically significant decrease, confirming that the observed effect results from fat reduction rather than loss of muscle, body protein, or body water.
• All safety indicators, including blood pressure, heart rate, ECG, hematology, and serum biochemistry, remain within normal ranges or show no clinically significant deterioration.
• The individual total effective rate in the test group is significantly higher than in the placebo group, and no serious adverse event attributable to the test article occurs.

Applications

The human feeding trial for weight-loss function serves multiple purposes across the functional food industry:

• Core efficacy and safety evidence for health food registration dossiers submitted to regulatory authorities under the national registration system.
• Scientific substantiation of slimming, body-fat-control, and weight-management claims for domestic and international product labeling.
• Formulation screening during research and development of functional ingredients such as dietary fibers, tea polyphenols, L-carnitine, conjugated linoleic acid, capsaicin, and white kidney bean extract.
• Supporting documentation for meal-replacement and sports-nutrition product categories where body-composition benefits are communicated.
• Post-market re-evaluation and claim maintenance for registered products with approved functions.
• Peer-reviewed scientific publication and competitive benchmarking of functional performance.

FAQ

Q: What is a human feeding trial for weight-loss function?

A: It is a randomized, double-blind, placebo-controlled intervention study in which overweight human volunteers consume a health food product for a defined period, and changes in body weight, body fat, and safety indicators are measured to substantiate a weight-loss or body-fat-control function claim.

Q: How long does the intervention last and how many subjects are required?

A: The intervention period is no fewer than 35 days, and the study generally requires at least 50 subjects in the test group and 50 in the placebo group, in accordance with the applicable evaluation standards.

Q: Who can participate as a subject?

A: Generally healthy adults aged 18 to 65 with a BMI of 24 or above who meet the inclusion criteria and none of the exclusion conditions, such as pregnancy, diabetes, thyroid disease, or recent use of weight-loss products.

Q: How is a positive result determined?

A: A positive result requires significant reductions in body weight, total fat mass, and body fat percentage compared with both baseline and placebo, no significant loss of lean body mass, an individual effective rate significantly higher than placebo, and no safety concerns in any clinical or laboratory indicator.

Q: Is ethics approval required?

A: Yes. The protocol must be reviewed and approved by an independent ethics committee, and every subject must sign an informed consent form before enrollment, in full compliance with the Declaration of Helsinki.

Q: Where is the trial conducted?

A: The clinical phase is carried out in qualified medical institutions authorized to perform human feeding trials, while laboratory analyses are completed by accredited third-party laboratories conforming to ISO/IEC 17025.

Q: What preparation is needed before starting the trial?

A: The sponsor must provide the product formula, quality standards, finished-product safety test reports, toxicological assessment reports, stability data, and a matched placebo before ethics submission and subject recruitment.