This was a two-year trial in which 322 people were randomly assigned to follow a Mediterranean diet, a low-fat diet, or a low-carb diet. By the study’s end, the low-carb group had lost the most weight – even though they were allowed to eat as much low-carb food as they needed to feel satisfied, while the other two groups followed calorie-restricted diets.
In this study, 148 people were randomized to consume a low-carb diet (less than 40 grams per day) or a low-fat diet (less than 30% of daily carbs per day) for one year. In addition to losing 3.5 kg (7.7 lbs) more than the low-fat group, the low-carb group also had greater improvements in HDL cholesterol, triglycerides, and other cardiovascular disease risk factors.
One of the most well-known weight-loss trials (often referred to as the A to Z study) involved randomizing overweight premenopausal women to eat either a low-carb (Atkins), moderate-carb (Zone), low-fat (Ornish), or low-calorie, portion-controlled (LEARN) diet for one year. At the end of the study, the women in the low-carb group had lost twice as much weight (4.7 kg, or 10.3 lbs) as the Ornish and LEARN groups and nearly three times as much as the women in the Zone group.