One of the concerns of the low-carb diet revolution that has swept the Western world over the last 20 years is that these diets may have a negative effect on long term health. In particular, some health professionals have suggested that individuals who adhere to a low carb diet tend to have higher cholesterol levels and therefore an increased risk of heart disease as a result of higher consumption of fat, particularly saturated fat. Fortunately, most studies have found low-carb diets to have little or no negative impact on cardiovascular health.
One study, published in The Journal of the American Medical Association, compared the impact of the Atkins, Zone, Weight Watchers, and Ornish diets on weight loss and cholesterol levels. The researchers found cholesterol changes on the Atkins diet were not significantly different to other diets. After a year on the Atkins diet, individuals experienced a 7.1mg/dL reduction in LDL cholesterol and a 3.4mg/dL increase in HDL cholesterol levels.
A second study, published in The New England Journal of Medicine, in 2003, involved 63 obese individuals who were randomly assigned to a low-carb or low-fat diet for a year. At the conclusion of the study, the researchers found that participants in the low-carb group lost 4.4% of their body weight compared to 2.5% in the low-fat group. Furthermore, participants in the low-carb group experienced an increase in HDL cholesterol levels of 11%, a decrease in triglyceride levels of 17%, while LDL and total cholesterol levels were largely unchanged.
Changes in total cholesterol levels need to be considered alongside changes in the ratio of total cholesterol to HDL cholesterol because this ratio is a much more accurate predictor of heart disease than total cholesterol by itself. If lower cholesterol levels are the result of a reduction in “good” HDL cholesterol rather than “bad” LDL cholesterol then that person will have increased their chances of developing heart disease despite having a lower cholesterol level.
The general scientific consensus seems to be that both low-carb and low-fat diets have favourable effects on an individuals cholesterol profile. Low-carb diets tend to raise HDL levels while low-fat diets tend to reduce LDL levels. The net effect in both cases is an improvement in the total/HDL cholesterol ratio.
If you choose to follow a low-carb diet plan and you have problems with high cholesterol, try to keep your consumption of saturated fats to below a quarter of total fat intake. For example, on an 1800 calorie diet with ratios of 20% carbohydrate, 40% protein, and 40% fat, your total fat intake would be 80 grams, so you should aim to consume less than 20 grams of saturated fat.
Ultimately, the most important factor on overall health is the level of weight loss you can achieve rather than whether a low-carb, balanced, or low-fat diet is used to achieve it.