The variety of successful dietary strategies employed by traditionally living populations provides an important perspective on the ongoing debate about how high-protein, low-carbohydrate regimens such as the Atkins diet compare with those that underscore complex carbohydrates and fat restriction. The fact that both these schemes produce weight loss is not surprising, because both help people shed pounds through the same basic mechanism: limiting major sources of calories. When you create an energy deficit--that is, when you consume fewer calories than you expend--your body begins burning its fat stores and you lose weight.
The larger question about healthy weight-loss or weight-maintenance diets is whether they create eating patterns that are sustainable over time. On this point it appears that diets that severely limit large categories of foods (carbohydrates, for example) are much more difficult to sustain than are moderately restrictive diets. In the case of the Atkins-type regimen, there are also concerns about the potential long-term consequences of eating foods derived largely from feedlot animals, which tend to contain more fat in general and considerably more saturated fats than do their free-ranging counterparts.