The results are at odds with the popularly held view that low-carb, high-protein diets are best for losing weight, a school of thought that peaked in acceptance with the Atkins diet about a decade ago. But there is an ongoing debate about what types of diet are most effective for treating overweight people, and in the food industry this has had an impact on products, particularly in the aftermath of the low-carb Atkins phenomenon. Many popular diets emphasize differing proportions of carbohydrate, protein or fat.
This latest study, entitled “Carbohydrate Intake and Overweight and Obesity among Healthy Adults”, examined the diets of a sample of 4,451 healthy Canadians. It found that those who ate the least carbohydrates were the most likely to be obese or overweight, while those who ate more carbohydrates were not only slimmer, but also tended to consume greater quantities of dietary fiber, more fruits and vegetables and less saturated fats.
Short term low-carb effect
“High-protein/low-carbohydrate diets bring about greater weight loss in the short-term than diets emphasizing overall energy restriction, but there is no difference between diets in weight loss achieved at the end of 1 year,” wrote the authors.
They found that the likelihood of overweight and obesity declined steadily as carbohydrate intake increased until it reached 290g to 310g per day, above which participants were more likely to be overweight or obese, but to a lesser extent that those with the lowest carbohydrate intakes.
The lowest risk of obesity and overweight was associated with those obtaining 47 to 64 percent of their energy intake from carbohydrates, while the greatest risk was with less than 47 percent.
Fiber and saturated fat challenge
Additionally, the study’s participants still did not consume enough fiber on average – 13g to 22g per day, compared to the recommended 38g for men and 25g for women – and ate too much saturated fat, which accounted for 7 to 14 percent of energy intake compared to the less than 7 percent recommended by Canadian health authorities.
“Thus, efforts to increase fiber and reduce saturated fat intakes, perhaps by avoiding energy-dense foods, may provide important health benefits in this population,” wrote the authors.
They added that overall caloric restriction remains the most effective way to reduce weight and wrote: “There is no consensus on the best dietary pattern to maintain optimal body weight”.
The US has a greater proportion of overweight and obese people than any other country, at over two-thirds, according to the Centers for Disease Control and Prevention. Excess weight has been associated with increased risk of heart attack, stroke, diabetes, cancer, arthritis and hypertension, among other conditions, and it is estimated to cost the government, families and organizations $117bn a year.
Source: Journal of the American Dietetic Association
July 2009, Vol. 109, issue 7, pp. 1165-1172
"Carbohydrate Intake and Overweight and Obesity among Healthy Adults"
Authors: Anwar T. Merchant, Hassanali Vatanparast, Shahzaib Barlas, Mahshid Dehghan, Syed Mahboob Ali Shah, Lawrence De Koning, Susan E. Steck.