Now, a small but carefully controlled study offers a strong hint that maybe Atkins was right: People on low-carb, high-fat diets actually can eat more.
The study, directed by Penelope Greene of the Harvard School of Public Health and presented at a meeting here this week of the American Association for the Study of Obesity, found that people eating an extra 300 calories a day on a very low-carb regimen lost just as much during a 12-week study as those on a standard lowfat diet.
Over the course of the study, they consumed an extra 25,000 calories. That should have added up to about seven pounds. But for some reason, it did not.
"There does indeed seem to be something about a low-carb diet that says you can eat more calories and lose a similar amount of weight," Greene said.
That strikes at one of the most revered beliefs in nutrition: A calorie is a calorie is a calorie. It does not matter whether they come from bacon or mashed potatoes; they all go on the waistline in just the same way.
"It doesn't make sense, does it?" said Barbara Rolls of Pennsylvania State University. "It violates the laws of thermodynamics. No one has ever found any miraculous metabolic effects."
In the study, 21 overweight volunteers were divided into three categories: Two groups were randomly assigned to either lowfat or low-carb diets with 1,500 calories for women and 1,800 for men; a third group was also low-carb but got an extra 300 calories a day.
The study was unique because all the food was prepared at an upscale Italian restaurant in Cambridge, Massachusetts, so researchers knew exactly what they ate. Most earlier studies simply sent people home with diet plans to follow as best they could...
Everyone's food looked similar but was cooked to different recipes. The low-carb meals were 5 percent carbohydrate, 15 percent protein and 65 percent fat. The rest got 55 percent carbohydrate, 15 percent protein and 30 percent fat.
In the end, everyone lost weight. Those on the lower-cal, low-carb regimen took off 23 pounds, while people who got the same calories on the lowfat approach lost 17 pounds. The big surprise, though, was that volunteers getting the extra 300 calories a day of low-carb food lost 20 pounds.
"It's very intriguing, but it raises more questions than it answers," said Gary Foster of the University of Pennsylvania. "There is lots of data to suggest this shouldn't be true."