Question: Do low carb diets work?

Question and AnswerQuestion and Answer

Research shows that low-carb diets work for weight loss and maintenance and lower cardiac risk.

Low Carbohydrate
Low Carbohydrate

Low carbohydrate diets have been around for centuries but for years this claimed benefits have been lacking in quality evidence to back their suggested use. The good news is that the evidence is growing to suggest that they are not only safe, but can be a part of a healthy weight loss diet for some. I would never recommend or suggest that any single diet is perfect for everyone because rarely does any diet work for everyone.

Previous studies comparing low-carbohydrate and low-fat diets have shown mixed results and they have not included a comprehensive behavioral treatment. In my opinion this is a clear disadvantage and is likely why they often resulted in suboptimal weight loss. In prior posts, I have pointed to low-carb as means for successful weight loss. Then again, there is plenty of research to show that lower fat diets work also. Low fat diets are just not as sexy in our modern culture because fat tastes great and it is easy to vilify sugar and carbohydrates.

The problem with most diets is that it is easy cut calories and lose weight, but there is limited evidence that we can maintain the weight loss over longer periods of time. Most weight loss is less than 6 months to a years. The good news is that research from 2010 does show that low carbohydrate diets can be a means for weight loss, weight maintenance, and a lower cardiac risk profile​[1]​.

The study from 2020 sought to evaluate the effects of 2-year treatment with a low-carbohydrate or low-fat diet, each of which was combined with a comprehensive lifestyle modification program. The study was a randomized trial across three academic medical centers and included 307 subjects with a mean age of just over 45 years. The intervention was a low-carbohydrate diet. The diet consisted of limited carbohydrate intake of 20 grams per day for 3 months in the form of low-glycemic index vegetables with unrestricted consumption of fat and protein.

After 3 months, participants in the low-carbohydrate diet group slowly increased their carbohydrate intake by 5 grams per day per wk until a stable. One the desired weight was achieved, the carbohydrate intake was stabilized. A low-fat diet consisted of limited energy intake of 1200 to 1800 Calories per day with a fat content of no more than 30%. <or=30%. Both diets were combined with comprehensive behavioral treatment.

The primary goal was weight loss of coarse, but they also looked at cardiac risk because the fat intake in low-card diets has often been linked to heart disease even if not entirely backed by research. The researchers used measures of success that included weight at 3, 6, and 12 months and serum lipid concentrations, blood pressure, urinary ketones, symptoms, bone mineral density, and body composition throughout the study.

Weight loss in the test group was approximately 11 kg or 23 pounds at one year and 7 kg or 15 pounds at two years. There were no differences in weight, body composition, or bone mineral density between the groups at any time point during the study. During the first 6 months, the low-carbohydrate diet group had greater reductions in diastolic blood pressure, triglyceride levels, and very-low-density lipoprotein cholesterol levels, and lesser reductions in low-density lipoprotein cholesterol levels. The low carbohydrate group tolerated the diet less well and were more like to quit than did the low-fat diet group. Also, the low-carbohydrate diet group had greater increases in high-density lipoprotein cholesterol levels at all time points and it was approximating a 23% increase at 2 years.

So what does this mean? Low carbohydrate diets work for weight loss and maintenance and this study confirms the results up to 2 years. Most importantly, the diet seems to confirm that low-carbohydrate diets also lower a dieter’s LDL and raise their HDL both of which should result in s significantly lower risk of heart disease. Successful weight loss can be achieved with either a low-fat or low-carbohydrate diet when coupled with behavioral treatment.

The bottom line: Low-carb diets work for weight loss and maintenance and should result in less, not more heart disease. Both diets were successful in this study but the low carb was superior. Intensive behavioral treatment was provided which may not be available to all trying to lose weight. patients with dyslipidemia and diabetes were excluded, and attrition at 2 years was high.


  1. [1]
    G. D. Foster, “Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet,” Ann Intern Med, p. 147, Aug. 2010, doi: 10.7326/0003-4819-153-3-201008030-00005. [Online]. Available:
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About the Author

I am a family physician who has served in the US Army. In 2016, I found myself overweight, out of shape, and unhealthy, so I made a change to improve my health. This blog is the chronology of my path to better health and what I have learned along the way.

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