JAMA Study Confirms Maintenance Benefits of Low Carb Diet
By Barbara Berkeley, MD
The debate about whether a calorie is a calorie rages on, but not I think, in the minds of most successful weight maintainers. The same may be said for successful dieters who reflexively cut carbohydrates from their menu when they start a weight loss plan. While their thought may be to reduce calories, something quite different may be occurring when they ditch the bread and pasta for meals of chicken breast and salad.
Too few scientific studies have looked at the metabolic differences that occur in response to differing nutrients. Some readers may find my continued harping on the insulin system simplistic, but it has been my way of conceptualizing a consistent observation: limiting carbohydrate in the diet to natural fruit and vegetable sources appears to decrease hunger, clamp down on cravings, preserve weight maintenance, and promote health. While I am well aware of those readers who say that they do perfectly well eating other carbs, I still think that they are likely to represent a minority. In my own experience, there is nothing so threatening to the maintenance of long term weight as a return to modern carb consumption. When patients come back to me with a significant regain, there has uniformly been a reassertion of carbs and carb craving in their lives.
The June 27th issue of JAMA has a study that comes from researchers at Harvard and Baylor . It is neatly done and quite thought provoking. The idea was to induce about a 13% weight loss in overweight men and women. These would-be maintainers were then placed on one of three diets whose calories were calculated to preserve that weight loss. But the types of calories in each diet were different and were constructed to follow one of three models. Each study subject was given each of the three diets in turn, with the order of the diets being random.
The maintenance diets were as follows:
Low Fat: This diet followed the more traditionally prescribed guidelines for weight control being low in fat and high in whole grains, fruits and vegetables. (60% carbs/20% Fat/20% protein)
Low Glycemic Index: This diet actually achieved a moderate (not low) glycemic load by replacing some grains and starches with healthy fats, fruits, vegetables and legumes. (40% carbs/ 40% fat/ 20% protein)
Very Low Carbohydrate: This diet was modeled on the Atkins diet. (10% carbs/ 60% fat/ 30% protein)
Each diet was eaten in random order for four weeks. The subjects were tested to determine whether their metabolic rate (the speed and efficiency of calorie burn) was affected by the varying nutrient compositions. They were also evaluated for insulin sensitivity, cortisol, leptin, thyroid hormone, and subjective levels of hunger and satisfaction among a number of other parameters.
The fascinating result was that both resting and total metabolic rate was significantly greater when people ate the very low carb diet. In fact, the difference in metabolic advantage between the low fat and low carb diet was about 300 calories per day, ďan effect corresponding with the amount of energy typically expended in 1 hour of moderate-intensity physical activity.Ē
In addition, the study revealed a number of other beneficial advantages to the low-carb diet. These included better sensitivity to the action of insulin, and improvement in markers for metabolic syndrome. Leptin is a hormone which is often invoked as a reason for failed maintenance. Leptin should theoretically decrease food intake and one would assume that higher levels would be a good thing. However we know that obese people (and obese lab animals too) have a resistance to leptin. Levels may be high but they donít work appropriately. In this study, leptin levels were lowest in the low carb group, but leptin sensitivity appeared to be restored by eating this way.
There were two negatives to the low carb diet, both related to inflammatory stress. Two stress markers were elevated in this diet: cortisol and C Reactive Protein. However, the diet used for the low carb choice was a 60% fat plan based on Atkins. We know that certain fats, particularly saturated fats, can be proinflammatory. Once again, there was no testing of another kind of low carb diet: a primal style diet that eliminates grains and starches but preserves fruits and vegetables and which uses lower fat protein choices. I donít need to tell you that my belief is that this diet would have triumphed over the others.
But enough of my biases. We finally have a study that shows that different foods create different responses in the body and that calories are only one property of food. The other properties of food can easily trump calories by activating differing pathways through digestion and metabolism.
A calorie is just a calorie thatís true, but unlike what weíve been led to believe, it is not the be all and end all of how the body burns or stores food. Can we finally begin to get past this simplistic and unhelpful maxim?
From Refuse to Regain email
I don't know about you - I have been eating low carb, paleo and it is working so well for me. Also for my family - my one son has eliminated the RA pain he was having.
CSTzone, Wpg, MB, CAN Leader Corrosion of Conformity, Winnipeg Sparklers, Positive Thinking.
Check out Corrosion of Conformity, we would love to have you join! www.sparkpeople.com/myspark/groups_individ
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