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In a face-off between a low-fat and a low-carbohydrate diet, neither reigned supreme.

According to the DIETFITS (Diet Intervention Examining The Factors Interacting with Treatment Success) trial, weight loss after 12 months was similar between the diet types, with an average weight loss of 11.68 pounds for the healthy low-fat (HLF) diet and 12.23 pounds for the healthy low-carbohydrate group (HLC) (mean between-group difference, 1.54 pounds, 95% CI -0.44 to 3.53 pounds).

The results, published online in , showed no significant interaction between the amount of weight loss, individual genotype responsiveness patterns -- a low-fat or low-carb-responsive genotype -- and appropriate matching to corresponding diet type (ß 1.38, -0.72 to 3.49, P=0.20), according to Christopher D. Gardner, PhD, of the Stanford Prevention Research Center in California, and colleagues.

Similarly, there was also no interaction between the extent of weight loss after a year with diet-insulin secretion (INS-30) (ß 0.08, -0.13 to 0.28, P=0.47).

A total of 609 adults were included in the trial, all of whom were considered to be overweight or obese at entry. Exclusion criteria included having diabetes; uncontrolled hypertension or metabolic disease; cancer; and diseases of the heart, kidney, or liver.

Following randomization into either an HLF or HLC dietary intervention, participants received 22 sessions over a 12-month period, led by registered dietitian health educators. The participants were initially instructed to reduce their total fat or carbohydrate intake to 20 g/day during the first 8 weeks of intervention, and then slowly added back either fat or carbs into their diet, not surpassing the lowest level of sustainable intake each participant could individually maintain.

"We made sure to tell everybody, regardless of which diet they were on, to go to the farmer's market, and don't buy processed convenience food ... Also, we advised them to diet in a way that didn't make them feel hungry or deprived -- otherwise it's hard to maintain the diet in the long run," said Gardner in a statement. "We wanted them to choose a low-fat or low-carb diet plan that they could potentially follow forever, rather than a diet they would drop when the study ended."

Insulin secretion and genotype patterns were assessed for all participants. Based on combinations of the three single-nucleotide polymorphism multilocus genotype responsiveness patterns, participants were grouped into being more sensitive to fat (40% of cohort), more sensitive to carbohydrates (30%), or sensitive to neither.

In the HLF group, 42.6% of participants had the low-fat genotype, while 27.2% had the low-carb genotype. A total of 37.5% of participants in the HLC diet had the low-fat genotype, while 31.9% had the low-carb genotype.

After 12 months, the average macronutrient distributions for the HLF and HLC groups were 48% versus 30% for carbs, 21% versus 23% for protein, and 29% versus 45% for fat, respectively.

Both diets also showed improvements in markers for body mass index, body fat percentage, waist circumference, lipids, blood pressure, and insulin and glucose levels after 12 months. However, the HLC diet showed significant improvements in HDL cholesterol and triglycerides compared with the HLF group.

Asked for her perspective, Reshmi Srinath, MD, director of the Weight and Metabolism Management Program at Mount Sinai Hospital and Icahn School of Medicine at Mount Sinai in New York City, who was not involved with the study, told 名媛直播, "The weight loss results are comparable to prior studies where we see weight loss really is dependent on compliance rather than the diet itself. But I was hoping to see some significant difference in the weight lost by those matched by genotype.

"The main limitation seems to be the report of physical activity and diet, but they tried to overcome this by using the Nutrition Data system for research for all diet recall," Srinath continued. "The study population is also unique in being very healthy, without comorbidity, and with access to high-quality food. This may not reflect the typical overweight or obese patient. This study furthers the need to investigate the role of genetics on weight loss and being able to tailor a diet to a particular individual based on their genetics."

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