• Change in insulin [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the intervention phase. ]
  Serum from fasting blood sample is used for measurement of insulin.
• Change in insulin-like growth factor-1 [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the intervention phase. ]
  Fasting blood sample for measurement of insulin-like growth factor-1.
• Change in mean blood glucose [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the intervention phase. ]
  Measured by a blood glucose monitor for 24-hour glucose monitoring during the 14-day intervention phase.
• Change in gut microbial compositions [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the intervention phase. ]
  Stool sample of subject is used for measurement of gut microbial compositions.
• Change in body weight [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the intervention phase. ]
  Body weight is measured according to the Physical Fitness and Health Surveillance of Chinese School Students by trained, certified study staff. It is measured to the nearest 0.1 kg.
• Change in body weight [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the self-maintenance phase. ]
  Body weight is measured by subject and reported by electronic questionnaire. It is measured to the nearest 0.1 kg.
• Change in waist circumference [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the intervention phase. ]
  Waist circumference is measured to the nearest 0.1 cm using a constant tension tape around the waist at 1 cm below the navel as the subject exhaled. It is calculated as the average value of two measurements.
• Change in waist circumference [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the self-maintenance phase. ]
  Waist circumference is measured by subject and reported by electronic questionnaire. It is measured to the nearest 0.1 cm using a constant tension tape around the waist at 1 cm below the navel as the subject exhaled. It is calculated as the average value of two measurements.
• Dietary energy intake [ Time Frame: From the baseline (the first day of the intervention phase) to the 14th day of the intervention phase. ]
  Daily dietary energy intake (kcals/day) is calculated by researchers using food weighing photos of the subject.
• Self-reported dietary adherence [ Time Frame: At the 14th day of the self-maintenance phase. ]
  Adherence to diet will be assessed with a electronic questionnaire in the self-maintenance phase.

The National China Health and Nutrition Survey revealed that 42% of overweight children had at least one cardiovascular metabolic risk, such as hyperglycaemia, dyslipidemia or hypertension. Non-pharmaceutical life style modifications are the recommended intervention to these subjects, including caloric restriction and increased physical activity. However, the problems of poor compliance and metabolic adaptation are well known. Evidences from a number studies in rodent models and human indicated that intermittent caloric restriction (ICR) may stimulate series reactions in human body, including improvement of insulin sensitivity, blood pressure, oxidative stress and inflammation, and may be easier to follow. Evidence from larger human studies is strongly encouraged, while the effects, safety and adherence in chidren and youth need to be studied.

This study is a randomized controlled trial of intermittent caloric restriction versus low carbohydrate diet in youth with cardiometabolic risk over one month period. The intervention is based on the 5:2 diet, which involves caloric restriction for 2 days (consecutive or nonconsecutive, 600kcal/d for male and 500kcal/d for female) per week and unrestricted eating during the other 5 days of the week. For control group, the subjects receive 7 days (consecutive or nonconsecutive) of low carbohydrate diet intervention during the 14-day intervention period,. Carbohydrate intake of low-carbohydrate diet should be controlled as ≤ 50g per day. Total trial duration is one month consisting of a 14-day intervention phase and a 14-day self-maintenance phase. During the maintenance phase, two follow-up electronic questionnaires were conducted.

The study aim to explore effects of the dietary interventions on cardiometabolic markers, inflammatory reaction, oxidative stress and gut microbiome in youth with cardiometabolic risk.

• Overweight
• Obesity
• Cardiometabolic Risk

• Behavioral: Intermittent caloric restriction

  The intervention is based on the 5:2 diet, which involves caloric restriction for 2 days (consecutive or nonconsecutive, 600kcal/d for male and 500kcal/d for female) per week and unrestricted eating during the other 5 days of the week.

  Total trial duration is one month consisting of a 14-day intervention phase and a 14-day self-maintenance phase. During the maintenance phase, two follow-up electronic questionnaires were conducted.

  Other Name: Intermittent fasting
• Behavioral: Low carbohydrate diet

  During the 14-day intervention period, the subjects receive 7 days (consecutive or nonconsecutive) of low carbohydrate diet intervention. Carbohydrate intake of low-carbohydrate diet should be controlled as ≤ 50g per day.

  Total trial duration is one month consisting of a 14-day intervention phase and a 14-day self-maintenance phase. During the maintenance phase, two follow-up electronic questionnaires were conducted.

• Behavioral: Health education on reducing the cardiometabolic risk
  Health education is conducted once a week during 14-day dietary intervention for all subjects. Health education including the understanding of cardiovascular disease, how to determine the cardiometabolic risk level, and the lifestyle intervention as caloric restriction and increased physical activity to promote health.

• Experimental: Intermittent caloric restriction
  Interventions:

  • Behavioral: Intermittent caloric restriction
  • Behavioral: Health education on reducing the cardiometabolic risk
• Active Comparator: Low carbohydrate diet
  Interventions:

  • Behavioral: Low carbohydrate diet
  • Behavioral: Health education on reducing the cardiometabolic risk

• Harvie MN, Pegington M, Mattson MP, Frystyk J, Dillon B, Evans G, Cuzick J, Jebb SA, Martin B, Cutler RG, Son TG, Maudsley S, Carlson OD, Egan JM, Flyvbjerg A, Howell A. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes (Lond). 2011 May;35(5):714-27. doi: 10.1038/ijo.2010.171. Epub 2010 Oct 5.
• Arnason TG, Bowen MW, Mansell KD. Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study. World J Diabetes. 2017 Apr 15;8(4):154-164. doi: 10.4239/wjd.v8.i4.154.

Inclusion Criteria:

Have at least one of the following cardiometabolic abnormalities:

1. Overweight or obesity (central obesity or general obesity)
2. Prediabetes: impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT)
3. Dyslipidemia
4. Elevated blood pressure

Criteria for cardiometabolic abnormalities:

1. Overweight or obesity

   For subjects (9 ≤ age ≤ 18 years) :

   • General obesity: Body mass index higher than the 85th percentile for overweight and the 90th percentile for obesity, based on the references for screening overweight and obesity in Chinese children and adolescents.

   • Central obesity: Waist circumference higher than the 90th percentile of the age and gender-specific reference for screening cardiovascular risk factors in Chinese children and adolescents.

   For subjects ( 19 ≤ age ≤ 30 years) :

   • General obesity: Body mass index between 24.0 and 27.9 kg/m2 for overweight and ≥28 kg/m2 for obesity.

   • Central obesity: Waist circumference ≥85cm for men and ≥80cm for female. Based on recommendation of overweight and obesity in Chinese adults.

2. Prediabetes:

   With IFG and/or IGT. IFG: fasting glucose from 5.6 to 6.9 mmol/L; IGT: 2-h glucose in the 75g oral glucose tolerance test from 7.8 to 11.0 mmol/L.

   Based on recommendation of American Diabetes Association.

3. Dyslipidemia:

   For subjects (9 ≤ age ≤ 18 years) :

   Triglycerides of ≥1.70 mmol/L or total cholesterol of ≥5.18 mmol/L or lowdensity lipoprotein cholesterol ≥3.37 mmol/L or highdensity lipoprotein cholesterol of ≤1.04 mmol/L. Based on recommendation in Chinese children and adolescents.

   For subjects ( 19 ≤ age ≤ 30 years) :

   Triglycerides of ≥1.7 mmol/L or total cholesterol of ≥5.2 mmol/L or lowdensity lipoprotein cholesterol ≥3.4 mmol/L or highdensity lipoprotein cholesterol of ≤1.0 mmol/L. Based on guideline for the management of dyslipidemia in Chinese adults.

4. Elevated blood pressure:

For subjects (9 ≤ age ≤ 18 years) :

Blood pressure higher than the 90th percentile of blood pressure age and gender-specific reference standards for Chinese children and adolescents, or blood pressure >120/80 mmHg.

For subjects ( 19 ≤ age ≤ 30 years) :

Systolic blood pressure≥120 mmHg and/or diastolic blood pressure ≥80 mmHg. Based on Chinese guidelines for the management of hypertension.

Exclusion Criteria:

1. Diagnosis of severe diseases such as cardiac insufficiency, severe malnutrition or immunodeficiency.
2. History of bariatric surgery.
3. Use of antiobesity drugs or supplements.