Low - carbohydrate diet (Atkins)

In consideration of the safety and efficacy of low-carbohydrate diets such as the Atkins diet:

• a systematic review of 94 studies of low-carbohydrate dietary interventions (1):
  • concluded that there was insufficient evidence to make recommendations for or against these diets
  • noted that the studies varied greatly in their design, diet duration and carbohydrate content, characteristics of the participants
• two subsequent randomised controlled trials compared low-carbohydrate diets with conventional low-fat diets in obese people (2,3) revealed:
  • weight loss was significantly greater with the low-carbohydrate diets than with the low-fat diets at six months
    • the significantly greater weight loss observed with the lowcarbohydrate diet at six months was not sustained in the one trial that followed participants for 12 months
    • drop-out rates in both diet groups were high
  • there have been concerns that low-carbohydrate diets may result in adverse cardiovascular, renal, hepatic and skeletal effects - due to accumulation of ketones and excessive consumption of animal proteins and fats
    • both of the above trials revealed some improvements in the lipid profile of participants using the low-carbohydrate diet compared with those using the conventional low-fat diet - however, these findings must be interpreted with caution (2,3)

A follow up of the study (2) at one year was undertaken to examine comparison of weight loss and metabolic changes in obese adults randomly assigned to either a low-carbohydrate diet or a conventional weight loss diet (4). The authors concluded that:

• participants on a low-carbohydrate diet had more favorable overall outcomes at 1 year than did those on a conventional diet
  • weight loss was similar between groups, but effects on atherogenic dyslipidemia and glycemic control were still more favorable with a low-carbohydrate diet after adjustment for differences in weight loss

Notes:

• a review (5) noted that:
  • it is uncertain whether the improvements seen in some aspects of the lipid profile have the same beneficial effect on cardiovascular outcomes when consuming a diet that is high in saturated fat. Also, the large amount of saturated fat and small amount of fruits, vegetables and fibre consumed on these diets could independently increase the risk of CHD
  • concerning low-carbohydrate diets the review concluded ".....Given the uncertainties over the efficacy, safety and sustainability of low-carbohydrate diets, there is currently insufficient evidence to support this approach to weight loss in preference to a nutritionally balanced, low-fat diet combined with exercise, as recommended by the British Dietetic Association (BDA). People considering low-carbohydrate diets should be made aware of this.... "
• a comparison of 4 different diets was undertaken (6):
  • compared with women who were assigned to follow diets having higher carbohydrate content, women assigned to the diet with the lowest carbohydrate content had more weight loss and more favorable changes in related metabolic risk factors at 2 and 6 months
  • greater weight loss for the Atkins diet continued through 12 months - this reached statistical significance in comparison with the Zone diet
  • no significant differences in weight loss at any time point among the Zone, LEARN, and Ornish diets
  • riglycerides, HDL-C, blood pressure, and measures of insulin resistance either were not significantly different or were more favourable for the very-low-carbohydrate groups
• in comparison of low-carbohydrate diet, low-fat diet (30% of calories from fat), Mediterranean diet (7):
  • in moderately obese adults, Mediterranean and low-carbohydrate dietes led to more weight loss than low-fat diet
  • low-carbohydrate diet increased HDL more than the low-fat diet
• effect of a plant-based low-carbohydrate ("Eco-Atkins") diet on body weight and blood lipid concentrations in hyperlipidemic subjects
  • a small study revealed that a low-carbohydrate plant-based diet (substituting plant based fats and proteins for animal fats and proteints) had lipid-lowering advantages over a high-carbohydrate, low-fat weight-loss diet in improving heart disease risk factors not seen with conventional low-fat diets with animal products (8)

Further details and advice on the best approaches to healthy weight control are available on the BDA website: www.bda.uk.com

Reference:

• (1) Bravata DM et al. Efficacy and safety of low carbohydrate diets: a systematic review. JAMA 2003;289:1837-50.
• (2) Samah FF et al. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med 2003;348:2074-81.
• (3) Foster GD et al. A randomized trial of a low-carbohydrate diet for obesity. N Eng J Med 2003;348:2082-90.
• (4) Stern L et al. The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one year follow-up of a randomized trial. Ann Intern Med 2004;140:778-85.
• (5) MeReC Extra Issue 11 (December 2003).
• (6) 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
• (7) Shai I et al. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med. 2008 Jul 17;359(3):229-41
• (8) Jenkins DJ, Wong JM, Kendall CW, Esfahani A, Ng VW, Leong TC, Faulkner DA, Vidgen E, Greaves KA, Paul G, Singer W. The effect of a plant-based low-carbohydrate ("Eco-Atkins") diet on body weight and blood lipid concentrations in hyperlipidemic subjects. Arch Intern Med. 2009 Jun 8;169(11):1046-54.