Do Low-Carb Diets Really Work?

Can You Lose Weight on a Low-Carb Diet?

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Do low-carb diets work? Anyone embarking on a new way of eating wants the answer to this question. And although we can usually find "success stories" associated with almost any diet, that doesn't really tell us what we want to know, which is the facts. (We've all seen those ads for a weight-loss miracle cure, with the tiny words at the bottom which say "results not typical".)

First, be clear on what you mean by a diet "working".

What are your goals? We tend to think of weight loss first, but reduced-carb diets are now being used to treat a number of conditions, as well as for prevention of diseases like diabetes. Weight loss will be the focus of this article, but there are lots of other health benefits that are associated with low-carb diets.

Low-Carb Diets Work for Weight Loss and More

 Forms of low-carb diets are some of the most popular weight-loss diets, and science bears out that in general, they are at least as effective, and usually more effective when compared to other weight-loss diets (which mainly focus on controlling calories). For example, a 2012 journal article reviewed the science and found 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 (and 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.

If the people in a study are more carefully chosen (NOT entirely random), so that people who are likely to benefit the most from low-carb eating are assigned to that diet, people tend to lose more weight. For example, here I describe a randomized study where the researchers went back and analyzed the data to see who did best on which diet.

The results were dramatic: even though the average weight loss was modest for the groups as a whole, people who had signs of insulin resistance (one sign of "sugar sensitivity") lost the most weight on the low-carb diet, and did very poorly on the high-carb diet. The people who were insulin sensitive (the opposite of insulin resistant) did well on either diet. So while randomized studies can give us valuable information, they often don't give us a strong indication of how much weight any one person is likely to lose.

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 we cannot trust our bodies' signals about hunger and satiety. Instead, we must ignore those signals and carefully and consciously regulate the amount of food we eat.

(This works for awhile, but often not for long, which is a whole other topic.) Carbohydrate reduction works differently (especially for people who are sensitive to carbohydrate), in that it helps regulate our appetite system so we 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. In addition, 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.

When I ask people what they like best about following a low-carb diet, they will often mention 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"?

When we hear about low-carb diets, it can be challenging to know what people are actually talking about! Diet studies have labeled everything from 5% to 45% of calories from carbohydrate as "low-carb". And, indeed, different amounts of carbohydrate are best for different people, due to something variously called "carbohydrate sensitivity", "carbohydrate tolerance", "metabolic resistance" and other terms. Basically, it has to do with how our bodies respond to sugar - the more problems we have with it the more likely that we will respond positively to eating less of it. (All carbohydrate breaks down into sugar in our bodies.) So how effective the diet partly depends 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 (or any other weight-loss diet, for that matter). I know people who have lost over a hundred pounds by eating low-carb, and kept it off over 5 years (which is the benchmark for permanent weight loss), and lots of people who have lost 50-70 pounds and kept is off for several years. But plenty of others lost more modest amounts of weight and got 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.) Also, just achieving a stable weight can be a big benefit, especially for people who were finding themselves getting heavier and heavier. My own weight, which is still well above "normal", has been stable for over 12 years, which is a huge relief. In addition, I have received many of the other typical health benefits, improved energy levels, and much more. My doctor tells me I would be diabetic by now if I wasn't following this way of eating.

Weight Loss Success Stories

OK, now you have the facts! But being successful on a diet isn't just about knowing the science. How about hearing some encouraging stories from people who have had success with low-carb eating? And then go on to find tips, recipes, and lots of information to help you try out a lower-carb life.


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

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.

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