Do Low-Carb Diets Really Work?

Losing Weight and Other Benefits of a Low-Carb Diet

Photo © Peter Dazeley/Getty Images

Do low-carb diets work? Anyone embarking on a new way of eating wants the answer to this question. Although you can find success stories associated with almost any diet, that doesn't tell you the facts you want to know. Those anecdotes may be the "results not typical" you see at the bottom of weight-loss miracle cure ads.

First, what are your goals? Reduced-carb diets are not only used for weight loss, but for the management of conditions like diabetes and other health benefits.

Here is the evidence that low-carb diets can be an effective way to lose weight.

Low-Carb Diets Work for Weight Loss and Possibly More

Forms of low-carb diets are some of the most popular weight-loss diets. Studies generally find that low-carbohydrate diets are at least as effective as other weight-loss diets, which are usually are reduced-calorie diets. Reviews of studies note that initial weight loss is often faster with a low-carb diet, but long-term weight loss is the same for all diets.

2012 journal article reviewed 17 high-quality well-controlled randomized diet studies which included a low-carb group. In analyzing these studies, they found that the people on the low-carb diets lost weight (usually more than the other diet groups), had lowered blood pressure, lower blood glucose, lower insulin, lower triglycerides, higher HDL ("good cholesterol"), and lower C-reactive protein, a marker of inflammation.

However, this study was comparing the subjects before and after, not with controls.

A Cochrane review of studies found that low-carbohydrate diets and calorie-based diets had the same effects on weight loss and cardiovascular risk factors. While some prior studies pointed to more beneficial effects for people with diabetes, this review did not.

However, it is reassuring that it appears that choosing a low-carb diet will have at least the same benefits as other low-calorie diets.

How Are Low-Carb Diets Different?

Low-carb diets function differently from other weight loss diets, in a way that seems to make it easier to lose weight once your body adjusts to the diet. 

Most weight-loss diets are based on the idea that you cannot trust your body's signals about hunger and satiety. Instead, you must ignore those signals and carefully and consciously regulate the amount of food we eat. Carbohydrate reduction works differently in that it helps regulate your appetite system so you naturally want to eat less. How it does this is not yet fully understood, but we do know that food which raises blood sugar more make people hungrier. Also, a low-carb diet lowers insulin levels in people who have high insulin. Since insulin regulates fat storage, many experts think that it makes it easier for the body to access stored body fat for energy.

People on low carb diets often say what they like best is not feeling hungry, not having food cravings, and having more stable energy levels compared to other types of diets. This seems to be true even after the weight loss phase of a diet.

How Much Carbohydrate is "Low"?

Diet studies have labeled everything from 5 percent to 45 percent of calories from carbohydrate as "low-carb." Indeed, different amounts of carbohydrate are best for different people, due to something variously called carbohydrate sensitivity, carbohydrate tolerance, metabolic resistance, and other terms.

All carbohydrate breaks down into sugar in your body. The more problems you have with the body's response to sugar, the more likely that you will respond positively to eating fewer carbohydrates. The effectiveness of the diet depends in part on how close it is to the amount of carbohydrate your body does best with.

This is why popular diets such as Atkins and South Beach try to help people find the best amount of carbohydrate for the individual.

How Much Weight Can You Lose?

The truth is that it's difficult to predict how much weight any one person will lose on a low-carb diet. Anecdotally, some people can lose a hundred pounds by eating low-carb and keep it off over five years (which is the benchmark for permanent weight loss). Many people have lost 50 to 70 pounds and kept it off for several years.

But plenty of others lose more modest amounts of weight and get discouraged. However, at the same time, they were often getting lots of other health benefits, such as lower blood pressure and blood sugar. These results are consistent with most research into weight-loss diets. Just achieving a stable weight can be a big benefit, especially for people who were finding themselves getting heavier and heavier.


Dutton GR, Laitner MH, Perri MG. Lifestyle Interventions for Cardiovascular Disease Risk Reduction: A Systematic Review of the Effects of Diet Composition, Food Provision, and Treatment Modality on Weight Loss. Current Atherosclerosis Reports. 2014;16(10). doi:10.1007/s11883-014-0442-0.

Lennerz BS, Alsop DC, et al. Effects of dietary glycemic index on brain regions related to reward and craving in men. American Journal of Clinical Nutrition. 98:3 (2013) 641-7.

McClain AD, Otten JJ, et. al. Adherence to a low-fat vs. low-carbohydrate diet differs by insulin resistance status. Diabetes, Obesity, and Metabolism. Jan;15(1) (2013) 87-90

Naude CE, Schoonees A, Senekal M, Young T, Garner P, Volmink J. Low Carbohydrate versus Isoenergetic Balanced Diets for Reducing Weight and Cardiovascular Risk: A Systematic Review and Meta-Analysis. PLoS ONE. 2014;9(7). doi:10.1371/journal.pone.0100652.

Santos FL, Esteves, SS, et al. Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obesity Review. 13:11 (2012) 1048-66.

Continue Reading