The objective of this study was to determine whether a putative genotype pattern (low-fat vs. low-carbohydrate), or insulin-secretion (related to insulin resistance),would help to explain which diet is best for whom in a comparison of a Healthy Low-Fat to a Healthy Low-Carb diet over a one-year period, in generally healthy, non-diabetic, overweight and obese adults.

Eligible candidates for this study meet the following criteria:

• Men and women in general good health
• Under 50 years of age (women must be premenopausal)
• Overweight
• Interested in losing weight
• Willing to be randomly assigned to follow either a Very Low-Fat or Very Low-Carbohydrate Diet for 12 months

The results of this study were published in JAMA in February, 2018. You can read the abstract here.

Among the 609 participants in the study, who collectively lost >6,500 pounds after one year, there was no average difference in weight loss between the two diet groups (Healthy Low Fat vs. Healthy Low Carb; on average 12 vs. 13 pounds, respectively) and neither the specific genotype pattern nor baseline insulin secretion levels was helpful in identifying which diet was better for whom. However, as anticipated, the range of weight change within both diet groups was dramatic – from losing ~60 pounds to gaining ~20 pounds. The investigators are continuing to explore the rich data set collected among these participants to identify other possible predisposing or mediating factors that could explain this wide range of response to these two popular weight loss diet approaches.