An interventional study of Low carbohydrate diet and Moderate carbohydrate diet in Obesity, sponsored by Boston Children's Hospital. Completed at 4 sites in United States. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2017-07-21.
Sponsored by Boston Children's Hospital · Not applicable, Interventional, and Basic science
This study will evaluate a potential physiologic mechanism underlying the effects of dietary composition on control of body weight
The challenge in maintaining long-term weight loss is well known, however new research suggests diet quality may be the driving factor. A pilot study from our group demonstrated that a higher carbohydrate-containing diet was associated with lower total energy expenditure during weight loss maintenance (Ebbeling et al). These findings will be confirmed in the ongoing Framingham State Food Study (NCT02068885): Following weight loss on a standard diet, 150 overweight or obese adults (aged 18 to 65 years) will be randomized to one of three weight-loss maintenance diets varying in carbohydrate to fat ratios for 20 weeks.
However, the specific mechanisms underlying the calorie-independent effects of diet remain unclear. Another study from our group demonstrated lower energy availability (calculated based on caloric content of circulating metabolic fuel concentrations) in the fasting and late post-prandial periods in 8 overweight or obese young adults who were maintained on a low-fat (high-carbohydrate) diet (Walsh et al). We hypothesize that this lower metabolic fuel availability on a high carbohydrate diet results in part from increased anabolic changes within the adipocyte, favoring fat storage in preference to oxidation.
We will invite subjects already enrolled in the Framingham State Food Study to participate, aiming for a total of 30 subjects (with the goal of approximately equal numbers per diet group following randomization to assigned test diet in the parent study). Participants will be admitted to a research unit for a 24-hour period during weight maintenance on the test diet, during which they will undergo frequent blood sampling for the measurement of circulating metabolic fuels, hunger and satiety ratings, while consuming their assigned diet meals. Each participant will also undergo two abdominal subcutaneous fat aspiration biopsies under local anesthesia, the first immediately following weight loss (before initiating the test diet) and the second during weight maintenance, in order to perform gene expression analyses on the adipose tissue. Our main outcomes will be a comparison in energy availability (the sum of energy in the major metabolic fuels in the blood) between diet groups in the late postprandial period and changes in adipose tissue gene expression within-individuals and by diet group assignment. Other outcomes will include differences in hunger and satiety ratings, total 24-hour energy availability, and specific metabolic fuel concentrations.
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Inclusion Criteria (as detailed in Framingham State Food Study, NCT02068885)
Additional Inclusion Criteria:
Exclusion Criteria:
Exclusion Criteria (as detailed in Framingham State Food Study, NCT02068885)
Additional Exclusion Criteria:
Behavioral: Low carbohydrate diet
Behavioral: Moderate carbohydrate diet
Behavioral: High carbohydrate diet
Composition (by proportion of calories) : 15% carbohydrate, 65% fat, 20% protein
Also known as: Composition : 15% carbohydrate, 65% fat, 20% protein
Feeding study. Composition (by proportion of calories): 40% carbohydrate, 40% fat, 20% protein
Feeding study. Composition (by proportion of calories): 60% carbohydrate, 20% fat, 20% protein
Late postprandial energy availability
Post-prandial energy availability calculated as the sum, in kcal/L, of energy from circulating metabolic fuels (glucose, non-esterified fatty acids, lactate and ketoacids), as measured during a 24 hr inpatient admission. Time of interest includes 2.5 - 5 hr in the postprandial period after breakfast, lunch and dinner.
Time frame: 10 - 15 weeks after initiation of test diets
Late postprandial energy availability, with lactate excluded
Post-prandial energy availability calculated as the sum, in kcal/L, of energy from circulating metabolic fuels (glucose, non-esterified fatty acids, and ketoacids), as measured during a 24 hr inpatient admission. Time of interest includes 2.5 - 5 hr in the postprandial period after breakfast, lunch and dinner. (Lactate is metabolized primarily by the liver, which uses this substrate to produce glucose. Thus, including lactate in the calculation of metabolic fuels may comprise "double counting" -- and not accurately reflect actual fuel availability to body tissues)
Time frame: 10 - 15 weeks after initiation of test diets
Fasting energy availability
Fasting energy availability calculated as the sum, in kcal/L, of energy from circulating metabolic fuels (glucose, non-esterified fatty acids, lactate and ketoacids), as measured during a 24 hr inpatient admission.
Time frame: 10 - 15 weeks after initiation of test diet
Total energy availability
Total energy availability calculated as the sum, in kcal/L, of energy from circulating metabolic fuels (glucose, non-esterified fatty acids, lactate and ketoacids), as measured during a 24 hr inpatient admission.
Time frame: 10 - 15 weeks after initiation of test diets
Hunger
Measured during a 24 hr inpatient admission.
Time frame: 10 - 15 weeks after initiation of test diets
Satiety
Measured during a 24 hr inpatient admission.
Time frame: 10 - 15 weeks after initiation of test diets
Glucose
Concentration during 24-hr inpatient admission
Time frame: 10 - 15 weeks after initiation of test diets
Non-esterified fatty acids
Concentration during 24-hr inpatient admission
Time frame: 10 - 15 weeks after initiation after test diet
Lactate
Concentration during 24-hr inpatient admission
Time frame: 10 - 15 weeks after initiation of test diets
Ketoacids
Concentration during 24-hr inpatient admission
Time frame: 10 - 15 weeks after initiation of test diets
Insulin
Concentration during 24-hr inpatient admission
Time frame: 10 - 15 weeks after initiation of test diets
Effect modification by insulin secretion
We will test for an interaction by insulin secretion (as measured by plasma insulin 30 minutes into a standard oral glucose tolerance test) of the relationship between diet and metabolic fuels concentration.
Time frame: 10 - 15 weeks after initiation of test diets
Adipocyte studies of anabolic status
Adipose tissue gene expression studies (assessed by mRNA levels of selected candidate genes involved in lipid storage, fatty acid and lipid biosynthesis, angiogenesis, inflammation). Change from baseline.
Time frame: 10 - 15 weeks after initiation of test diets
Adipose tissue histology
Change from baseline.
Time frame: 10 - 15 weeks after initiation of test diets
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