Calorie Restriction Intervention Induces Enterotype-associated BMI Loss in Nonobese Individuals

Calorie restriction (CR), which has the potential effect on weight loss and blood amino acids, has been demonstrated to associate with gut microbiota in humans, especially in obese individuals. However, studies for simultaneously evaluating enterotype-dependent impacts of CR on the gut microbiota and blood amino acids in nonobese individuals are still limited.

Here, 41 nonobese individuals received a 3-week CR diet with approximately 50% fewer calories than a normal diet. The investigators measured individuals' BMI and blood amino acid concentration, along with the gut microbiota before and after the intervention. In this trial, 28 Enterotype Bacteroides (ETB) subjects and 13 Enterotype Prevotella (ETP) subjects were identified before the intervention.

The purpose of this intervention study is to evaluate the effect of calorie restriction on BMI loss, amino acid, and gut microbiota in healthy volunteers of two different enterotypes and provide useful insights for potential application of gut microbiome stratification in personalized nutrition intervention.

1. Volunteer Recruitment

   Volunteer-wanted posters were propagated at the China National Gene Bank in Shenzhen from March to April 2017. A non-obese healthy volunteer was considered if his/her BMI less than 28 kg/m2. 50 individuals met all the criteria and were recruited in this study, and 41 individuals (24 females and 17 males aged 30 ± 6 years old) completed the whole intervention. The study was approved by the institutional review board on bioethics and biosafety of BGI-Shenzhen, Shenzhen (NO. BGI-IRB 17020). All participates were fully informed of the design and purpose of this intervention study and signed a written informed consent letter.
2. Experiment Process

   The study included a one-week run-in period (baseline) and a three-week CR dietary intervention period. During the first week (run-in period), all healthy volunteers consumed their usual diet and were encouraged to avoid yogurt, high-fat foods, and alcohol. The CR diet was comprised of \~50% calories of a normal-calorie diet (female, 1000kcal/day; male, 1200kcal/day). It was designed with carbohydrate, fat, and protein as approximately 55%, 30% and 15% of the total energy intake respectively, according to the Dietary Guidelines for Chinese Residents (2016) and nutritionally balanced and a recent large nutritional study in China. Common foods in low-calorie diets such as rice, vegetables, eggs, pork, and beef were prepared in the investigators' study center to control experimental variables introduced by different foods and calorie estimation errors.

   Traditional Chinese cooking style - boiled, stir-fried and stewed, were applied for the foods. For each meal, digital scales were used to measure the nutritional and caloric values of different foods and total meal for males and females respectively.
3. Sample and Data Collection

BMI, blood and fecal samples of each volunteer were collected at the investigators' study center at baseline and after the 3-week CR intervention. BMI was measured via the clinic scale. The concentrations of 31 amino acids and derivatives in the fasting serum samples were measured by LC-MS/MS. The gut microbial composition was determined using shotgun metagenomics sequencing of fecal DNA.

Eligibility Criteria:
Inclusion Criteria:

* BMI less than 28 kg/m2 and more than 18 kg/m2;
* without antibiotics in the recent 2 months;
* regular eating and lifestyle patterns;
* no international travel in the recent 3 month;
* without hypertension, diabetes mellitus, gastrointestinal disease and other severe auto-immune disease;
* without prebiotic or probiotic supplements in the recent 2 months;

Exclusion Criteria:

* with antibiotics in the recent 2 months;
* Failure to comply with experimental requirement;