It's an old debate — is weight loss all about limiting what you eat? The answer is not a definitive "yes." In fact, there's more evidence to the contrary.

It is clear that weight gain is not caused by what popular diet and health gurus say it is — eating too much fat, not exercising enough and eating too many calories. A recent study published in the journal PLOS Medicine has reported the rise of obesity in an Algerian refugee camp where people are not getting enough nutrition.

The simplest formula for obesity

Obesity is caused primarily by eating too many carbohydrate foods.

Consider the statement of Carlos Grijalva-Eternod, lead-author, UCL Institute of Child Health, regarding the obesity rate in this study of Sahrawi refugees based in four camps near Tindouf city in Algeria:

A number of reasons may account for these trends. This traditionally nomadic population itself once favoured larger women, and has an excessive sugar consumption habit. However, other factors come into play, such a predominance of starchy foods, pulses and blended foods in food assistance packages, but with few, if any, fresh or dried vegetables and fruit. We need to find ways of boosting the supply of fresh produce to improve the adequacy and diversity of their diets. (Obesity and under-nutrition prevalent in long-term refugees, University College of London, Oct 3, 2012)

Not an empty theory

So here we have a working model showing that high carbs and low vegetables lead to obesity. It's what bestselling author Gary Taubes has been arguing with the experts, including the American Heart Association, until he's blue in the face.

Why, then, does it seem that calorie-restricted and low-fat diets really work? Taubes explains:

Virtually any diet that significantly restricts the number of calories consumed, even a diet that is described as low-fat (because the subjects are instructed to reduce the proportion of fat calories they consume), will cut the total amount of carbohydrate calories consumed as well. This is just simple arithmetic. If we cut all the calories we consume by half, for instance, then we're cutting the carbohydrates by half, too. And because these typically constitute the largest proportion of calories in our diet to begin with, these will see the greatest absolute reduction. If we preferentially try to cut fat calories, we'll find it exceedingly difficult to cut more than 400 or 500 calories a day by reducing fat — depending on how much fat we were eating to begin with — and so we'll have to eat fewer carbohydrates as well.

Put simply, low-fat diets that also cut significant calories will cut carbohydrates significantly as well, and often by more than they cut fat." (Taubes, Gary, Calories, fat or carbohydrates? Why diets work (when they do), garytaubes.com, Dec 13, 2010.)