Even if people can handle the side effects of the diet, there are no data to show that the initial rapid weight loss on the Atkins Diet can be maintained long term. Many of the studies on the Atkins Diet have lasted only a few days; the longest the Atkins Diet has ever been formally studied is one year.
There have been 4 such yearlong studies and not a single one showed significantly more weight lost at the end of the year on the Atkins Diet than on the control “low fat” diets.[213-215,523] In the yearlong comparison of the Atkins Diet to Ornish’s diet, Weight Watchers, and The Zone Diet, the Atkins Diet came in dead last in terms of weight lost at the end of the year. Ornish’s vegetarian diet seemed to show the most weight loss. The Atkins website had no comment.
Noting that by the end of the year, half of the Atkins group had dropped out, and those who remained ended up an unimpressive 4% lighter, Fat of The Land author Michael Fumento commented, “do you really think any of them could sell a single book copy, much less as many as 15 million (for Atkins), by admitting to a 50 percent drop-out rate in one year with a mere five percent of weight loss among those left?”
Ornish’s vegetarian (near-vegan) diet has been formally tested for years. Even though the diet was not even designed for weight loss, after five years most of the Ornish adherents were able to maintain much of the 24 pounds they lost during the first year “even though they were eating more food, more frequently, than before without hunger or deprivation.”
Another of the year-long studies also compared a low fat vegetarian (vegan) diet to the “Atkins Diet.” Those who ate as much as they wanted of the vegan diet lost an average of 52 pounds–60% more than those reportedly on the Atkins diet lost. This is consistent with what research we have on vegans themselves. Vegans are vegetarians that exclude all saturated animal fat and cholesterol from their diet.
The biggest study on vegans to date compared over a thousand vegans in Europe to tens of thousands of meateaters and vegetarians. The meateaters, on average, were significantly heavier than the vegetarians, who in turn were significantly heavier than the vegans. Even after controlling for exercise, smoking, and other nondietary factors, vegans came out slimmest in every age group. Less than 2% of vegans were obese.
In a snapshot of the diets of 10,000 Americans, those eating vegetarian were the slimmest, whereas those eating the fewest carbs in the sample weighed the most. Those eating less carbs were on average overweight; those eating vegetarian were not.
Vegetarians may have a higher resting metabolic rate, which researchers chalk up to them eating more carbs than meateaters (or possibly due to enhanced adrenal function). At the same weight, one study showed that vegetarians seem to burn more calories per minute just by sitting around or sleeping than meateaters–almost 200 extra calories a day. Although earlier studies didn’t find such an effect, if confirmed, that amounts to the equivalent to an extra pound of fat a month burned off by choosing to eat vegetarian.
The only other two formal yearlong studies found that although the initial drop in weight on Atkins was more rapid, weight loss on the Atkins Diet reversed or stalled after 6 months. The longer people stay on the Atkins Diet, the worse they seemed to do.[226-227] None of the four longest studies on the Atkins Diet showed a significant advantage over just the type of high carbohydrate diets Atkins blamed for making America fat.
Anyone can lose weight on a diet; the critical question is whether the weight loss can be maintained and at what cost. If low carb diets really did cure obesity, the original in 1864 would have eliminated the problem and no more diet revolutions would be necessary. Short-term weight loss is not the same thing as lifelong weight maintenance.