And let me preface all of this to say that I don’t need convincing. I have been successfully been maintaining my weight within five pounds for nearly two years, this time around. But if you want to look at the medical evidence, as it is constantly changing, why not? I think it’s good to be informed, and it feels good to get some validation, as well. It works for me. That’s enough.
Meta-analysis is a method to succinctly summarize and combine the results from multiple individual studies. The following meta-analyses of low carbohydrate diets are limited to randomized controlled trials that directly compare low carbohydrate diets to other diets. Some of the studies listed above are randomized controlled trials and are included in these meta-analyses.
A recent meta-analysis that included randomized controlled trials (from January 1, 1980 to February 28, 2005) published after the Cochrane review found that “low-carbohydrate, non-energy-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to 1 year. However, potential favorable changes in triglyceride and high-density lipoprotein cholesterol values should be weighed against potential unfavorable changes in low-density lipoprotein cholesterol values when low-carbohydrate diets to induce weight loss are considered.”
A more recent meta-study of randomized controlled studies (from January 2000 to March 2007) that compared low-carbohydrate diets to low-fat/low-calorie diets found that measurements of weight, HDL cholesterol, triglyceride levels and systolic blood pressure were significantly better in groups that followed low-carbohydrate diets. The authors also found a higher rate of attrition in groups with low-fat diets. They conclude that “Evidence from this systematic review demonstrates that low-carbohydrate/high-protein diets are more effective at 6 months and are as effective, if not more, as low-fat diets in reducing weight and cardiovascular disease risk up to 1 year.” They also call for more long-term studies.
A 2012 systematic review studying the effects of low-carbohydrate diet on weight loss and cardiovascular risk factors showed the LCD to be associated with significant decreases in body weight, body mass index, abdominal circumference, blood pressure, triglycerides, fasting blood sugar, blood insulin and plasma C-reactive protein, as well as an increase in high-density lipoprotein cholesterol (HDL). Low-density lipoprotein cholesterol (LDL) and creatinine did not change significantly. The study found the LCD was shown to have favorable effects on body weight and major cardiovascular risk factors (but concluding the effects on long-term health are unknown). The study didn’t compare health benefits of LCD to low-fat diets.
A meta-analysis published in the American Journal of Clinical Nutrition in 2013 compared low-carbohydrate, Mediterranean, vegan, vegetarian, low-glycemic index, high-fiber, and high-protein diets with control diets. The researchers concluded that low-carbohydrate, Mediterranean, low-glycemic index, and high-protein diets are effective in improving markers of risk for cardiovascular disease and diabetes.
While there are many other studies published, and some seem contrary to Low-carb safety and effectiveness, the New England Journal of Medicine study, published most recently, is the one I am leaning on most heavily. The only study I found disturbing was the one about kidney health, a few years back. It seems to be isolated, however.