Recent research has revealed that low carbohydrate diets can be an effective way to help some people lose weight over the short term, without any known detrimental side effects (such as elevated lipids or blood pressure). But a new study comparing three popular diets – Atkins, Ornish and South Beach – showed that the Ornish and South Beach diets lowered low-density lipoprotein (LDL, referred to as “bad” cholesterol), whereas levels increased on the Atkins.
Eighteen healthy subjects followed each diet in a manner that kept their weight stable for four weeks, followed by a four-week washout period. At the completion of each diet phase, diet records were analyzed, fasting blood sampled, and brachial artery reactivity measured (this provides insight into the flow of blood in the brachial arteries, a measure of overall risk of atherosclerosis).
Compared to baseline levels, the Ornish diet resulted in a 16.6% drop in LDL cholesterol; on the South Beach diet it dropped 11.8%. In comparison, LDL increased 8.1% on the Atkins diet. The brachial artery measurements were inversely linked to saturated fat intake, meaning the more saturated fat in the diet, the greater the restriction of flow of blood in the arteries. This correlates well with findings from other studies linking a high saturated fat diet to compromised brachial artery reactivity. The Atkins diet is typically rich in foods high in saturated fat, such as animal protein sources.
The authors concluded that during weight maintenance, less favorable biologic effects were observed when dieters follow the Atkins diet compared to South Beach or Ornish. This could be especially detrimental to people who are obese and have other risk factors for coronary artery disease. More research needs to be conducted in this population.
Nutrition Tip: If you prefer a low-carbohydrate approach to weight loss and maintenance, take steps to choose lower saturated fat food sources, such as lean cuts of meat, fish, skinless poultry, egg substitutes, and low fat cheeses. And remember to bump up low-carbohydrate plant foods like colorful, fresh vegetables.
Source: Miller M, Beach V, et al. Comparative effects of three popular diets on lipids, endothelial function, and c-reactive protein during weight maintenance. JADA 2009;109:713-717.
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Written by Melissa Ohlson, M.S, R.D., L.D., Preventive Cardiology and Rehabilitation.