CMAJ • November 21, 2006; 175 (11). doi:10.1503/cmaj.1060145.
© 2006 CMA Media Inc. or its licensors
All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association.
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Letters

Diet and weight loss

Irene Strychar

Department of Nutrition, Faculty of Medicine, Research Centre of Notre-Dame Hospital, Centre hospitalier de l'Université de Montréal, Université de Montréal, Montréal, Que.

[The author responds:]

In my review of low-carbohydrate diets in the management of weight loss,1 the statement about the depletion of glycogen stores and induction of gluconeogenesis ("whereby lean tissue is used to produce glucose as an energy source for the brain") refers specifically, as noted in the same paragraph, to the initiation of an Atkins diet, which limits carbohydrate intake to as little as 20 g/day. Soon after, as ketogenesis sets in, glucose is indeed displaced by ketone bodies as the predominant fuel for the brain, thus reducing the need for glucose synthesis from amino acids and sparing muscle mass.

Randomized controlled studies,2–4 as referenced in my review, have shown that low-carbohydrate diets, with not-intended or intended similar calorie restrictions, reduce lean body mass more than low-calorie diets. The calorie intake, the protein and carbohydrate content of the diet, the duration of the diet, the compliance to a restricted amount of carbohydrates to sustain ketoacidosis, and the age, physical activity and clinical condition of the subject are all factors that influence changes in lean body mass. It is not surprising, therefore, that articles such as those cited by Anssi Manninen indicate other effects on lean body mass status, which explain current controversies and justify further research.

REFERENCES

  1. Strychar I. Diet in the management of weight loss. CMAJ2006;174(1):56-63.
  2. Brehm BJ, Seeley RJ, Daniels S, et al. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrinol Metab 2003;88:1617-23.[Abstract/Free Full Text]
  3. Yancy WS, Olsen MK, Guyton JR, et al. A low-carbohydrate, ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia. Ann Intern Med 2004;140:769-77.[Abstract/Free Full Text]
  4. Meckling KA, O'Sullivan C, Saari D. Comparison of a low-fat diet to a low-carbohydrate diet on weight loss, body composition, and risk factors for diabetes and cardiovascular disease in free-living, overweight men and women. J Clin Endocrinol Metab 2004;89:2717-23.[Abstract/Free Full Text]




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