Dietary Carbohydrate and Internal Body Fat (CARBFUNC)

Haukeland University Hospital

Status: Completed

Conditions: Adiposity

Treatments: Behavioral: Cellular carbohydrate diet; Behavioral: Low-carbohydrate high-fat diet; Behavioral: Acellular carbohydrate diet

Study type: Interventional

Funder types: Other

Identifiers

NCT03401970

2017/621

Details and patient eligibility

About

This is a 2-year randomized controlled trial to test the effect of dietary carbohydrates, both quality and quantity, on changes in internal body fat mass. Up to 250 women and men with obesity are recruited in Bergen, Norway, and randomized to one of the following normo- and isocaloric dietary patterns (same amount of protein, polyunsaturated fatty acids and moderate energy, 2,000 - 2,500 kcal per day): 1) a low-fat high-carbohydrate diet primarily with refined (e.g., flour-based) carbohydrate sources, 2) a low-fat high-carbohydrate diet based on minimally refined (e.g., cellular) carbohydrate sources, and 3) a very-high-fat low-carbohydrate diet.

Full description

Obesity, and high internal fat storage in particular, represents a tremendous and increasing health challenge across the world, and is linked to the recent introduction and globalization of an ultra-processed food supply largely based on refined carbohydrates. However, more high-quality studies are needed to directly assess the role of carbohydrate quality in abdominal adiposity. We also need studies with greater long-term adherence to prescribed food profiles, which may be achievied with the help of new electronic tools such as meal planning applications.

The participants select and plan all meals among a list of carefully designed options, using an application/recipe booklet developed for the study. Each recipe/meal/snack is designed to fully comply with the overall macronutrient- and dietary profile for the respective groups. We will further instruct the participants to record their meal choices during three days every 14 days, and to record all deviations throughout the intervention.

Enrolled participants are invited to study visits at baseline and after 3, 6, 9, 12 and 24 months. At all or some of these time points, the participants provide biological samples (blood, urine and feces, and for some, adipose and/or muscle tissue) and undergo phenotyping, e.g., measurement of body weight and fat mass by bioelectrical impedance analysis and low-radiation CT imaging, and a standardized meal test with blood sample collection up to 4 hours postprandially. In addition, participants will be asked to fill out a collection of questionnaires that assess quality of life, motivation, fatigue, gastrointestinal health, appetite and physical activity. We ask the participants to maintain the same level of physical activity throughout the study.

The primary outcome measure is change in internal body fat mass (visceral adipose tissue) measured by CT imaging. Secondary outcome measures include change in 2-hour postprandial serum concentrations of insulin, change in 4-hour postprandial serum concentrations of triacylglycerols, and change in fecal microbiota composition measured by 16S sequencing.

Enrollment: 150 patients

Sex: All

Ages: 20 to 55 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• Body-mass index (BMI) equal to or above 30 kg/m2 and/or waist circumference equal to or above 102 cm for men and 88 cm for women
• Weight stable during the last 2 months before start of the study (less than 5 % change in body weight up or down)
• No known diabetes or consumption of diabetes medication
• Desire to follow a specified dietary pattern using specific recipes throughout the time of the study period
• Ability to periodically record food intake using a specially designed app for the study

Exclusion criteria

• Use of statins and/or diabetes medication
• Recent surgical or antibiotics treatment during the last 2 months before start of the study
• Chronic inflammatory bowel disease
• Serious disease
• Smoking
• Pregnancy or breast feeding
• Alcohol consumption during the study of more than 2 alcohol units per day (1 unit = 15 ml (12.8 g) pure alcohol)

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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150 participants in 3 patient groups

Acellular carbohydrate diet

Active Comparator group

Description:

Prescribed dietary pattern. Carbohydrates from acellular sources, e.g., refined flour/bakery products, at least 500 grams of fruits/vegetables per day, and a macronutrient composition within typical nutritional recommendations for the general population.

Treatment:

Behavioral: Acellular carbohydrate diet

Cellular carbohydrate diet

Experimental group

Description:

Prescribed dietary pattern. Carbohydrates from cellular sources, e.g., root vegetables, fruits, whole-grain rice, non-flour grain products, at least 500 grams of fruits/vegetables per day, and a macronutrient composition within typical nutritional recommendations for the general population similar to the acellular carbohydrate diet.

Treatment:

Behavioral: Cellular carbohydrate diet

Low-carbohydrate high-fat diet

Experimental group

Description:

Prescribed dietary pattern. Energy largely from fat, cellular carbohydrate sources, and otherwise similar food types as in the acellular/cellular carbohydrate diets including at least 500 grams of fruits/vegetables per day.

Treatment:

Behavioral: Low-carbohydrate high-fat diet