While some doubt the benefits of controlling carbohydrate intake, the fact of the matter is that there is now abundant scientific evidence that this approach is generally effective for the purposes of weight loss, while at the same time helping to improve biochemical markers of chronic disease, such as blood sugar levels and levels of blood fats, such as triglycerides.
In a new study presented at the American Diabetes Association symposium held in Chicago recently, the effects of low-carb eating were compared to a diet restricted in calories and fat in a group of elderly obese individuals suffering from type 2 diabetes [1]. The study lasted for a total of six months. At the end of this, the low-carbers had lost an average of 15 lbs. in weight, compared to an average of 11.4 lbs. in the low fat group. This difference was statistically significant.
In addition, though, those restricting carbohydrate saw decreases in their triglyceride and blood sugar levels that were, again, statistically significantly compared to the low-fat eaters.
There are sound biochemical reasons why they offer potential not just for weight loss, but other health benefits, too. Key to understanding how this can be relates to the fact that many starchy carbohydrates cause quite brisk and sustained release of sugar into the bloodstream. The sky-rocketing blood sugar levels starchy carbohydrates tend to invoke will induce the pancreas to secrete copious quantities of insulin—the hormone chiefly responsible for tempering sugar levels in the bloodstream. Yet, while essential to life, insulin has the capacity to stimulate the production of fat within the body, and can also inhibit of the breakdown of fat.
Their ability to cause gluts of insulin mean that while starchy staples we are encouraged to have our fill of may not be fatty, they nonetheless have considerable capacity to be fattening.
Bearing all this in mind, it should come as no surprise that low-carb diets can be effective for those seeking to lose weight. But how do such diets compare with the more conventional low-fat approach endorsed by many doctors and dieticians? To date, six trials (included the one discussed above) have pitted low-carbohydrate against higher-carb/lower-fat regimes over the medium to long term. All six of these studies found that weight loss after six months was significantly greater in the low-carbohydrate group than in the low-fat group. Three of these studies lasted for a year, at which point there was no significant difference in results. However, in one of these studies the individuals failed to restrict carbohydrate intake to the extent advised, and in the other dietary compliance was not checked at all. Because of these limitations, these studies cannot be used to judge the true effectiveness of low-carb eating in the long term. In the final yearlong study, carb restriction (Atkins' diet) resulted in about twice the weight loss of lower fat regimes (Ornish and LEARN diets) [2].
In one review, the effects of several lower and higher carbohydrate diets were compared [3]. Overall, lower carbohydrate diets were found to bring about an average weight loss of 27.3 lbs., compared with just 7.5 lbs. on the higher carbohydrate regimes.
Taken as a whole, the evidence suggests that carb-control offers considerable potential as a weapon in the battle of the bulge.
References:
1. Radulian G, et al. The effects of low carbohydrate diet as compared with a low fat diet in elderly patients with type 2 diabetes.
2. Gardner CD, et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007 Mar 7; 297(9): 969-77.
3. Bravata DM, et al. Efficacy and safety of low-carbohydrate diets a systematic review. JAMA 2003; 289(14): 1837-1850
Dr. John Briffa is a London-based doctor, author, and health writer with an interest in nutrition and natural medicine.
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