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Adherence beats diet type
Adherence and weight loss
Those meta-analyses found all the popular diets about equally poor for long-term weight loss, and none did better on adherence overall. Sorted from lowest adherence to best, people lost more weight the more closely they followed their diet.
Calorie-matched studies
Calorie-matched comparisons point the same way. For time-restricted eating versus none, there appears to be no difference in weight loss, fat loss, or most biomarkers of health when calories are equated. Low carb versus low fat shows no difference in fat loss either, once protein and calories match. A 2017 meta-analysis by Kevin Hall covered 22 such studies in which every participant was given their food, which keeps adherence high.
Why adherence fades
Adherence fades in every diet study once the honeymoon period passes: after a few months, people drift off whichever diet they began with. Studies where a dietitian talks with participants weekly tend to hold adherence better, but they are expensive to run. Weight loss needs some form of restriction, whether on a nutrient, on eating time, or on calories, and the forms feel different to different people.
Which trials compared big-name diets head to head?
In a 2005 JAMA trial led by Michael Dansinger, 160 adults were assigned to Atkins, Zone, Weight Watchers, or Ornish. After a year, average weight loss was modest and similar across the four diets. Each diet's results tracked how closely participants stuck to it, not which diet it was.
What did the DIETFITS trial show?
In 2018, Christopher Gardner and colleagues at Stanford published the DIETFITS trial in JAMA. It randomized 609 adults to a healthy low-fat or healthy low-carbohydrate diet for 12 months. Average weight loss was 5.3 kilograms on low-fat and 6.0 kilograms on low-carbohydrate, a difference that was not statistically significant. Neither a genotype pattern nor insulin response predicted who did better on which diet.
What do time-restricted eating trials show?
In a 2020 randomized trial in JAMA Internal Medicine, Kelsey Lowe and colleagues at UC San Francisco compared eating within an eight-hour window with eating throughout the day. After 12 weeks, the groups did not differ significantly in weight loss. The time-restricted group lost some lean mass. The study had 116 participants.
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