Low-carbohydrate diet

DEFINITION: Weight loss and maintenance through diets that are low in carbohydrates.

Overview

Mainstream groups such as the American Heart Association and the American Dietetic Association traditionally endorse a unified set of dietary guidelines for people who wish to lose weight: eat a low-fat diet and cut calories. However, many popular weight-loss and diet books take a very different approach. The Atkins diet, the Zone diet, Protein Power, and numerous other dietary approaches reject the low-fat guideline. Instead, these methods recommend cutting down on carbohydrates, whether in specific forms such as refined grains and added sugars or altogether. According to proponents of these theories, when a person reduces the carbohydrates in their diet (and, correspondingly, increases protein or fat, or both), that person will find it much easier to reduce calorie intake and may even lose weight without cutting calories.

The controversy over these contradictions has been heated. Proponents of the low-fat diet claim that low-carbohydrate (low-carb) diets are ineffective and even dangerous, while low-carb proponents say much the same about the low-fat approach. However, an article published in the Journal of the American Medical Association suggests that neither side has a strong case. Researchers concluded, essentially, that a calorie is a calorie, regardless of whether it comes from a low-carb or a low-fat diet. They did not find any consistent evidence that the low-carb diet makes it easier to lose weight than the low-fat diet, but neither did they find any consistent evidence for the reverse. Furthermore, the authors of the review did not find any compelling reason to conclude that low-carb diets are unsafe, although they did point out that the long-term safety of such diets remained unknown.

A 2021 narrative review published in Nutrients found that the low-carb diet was effective for remission of type 2 diabetes mellitus and reducing fat mass for up to six months, but that the effectiveness and practicality of the diet were limited over the long term. A systematic review and meta-analysis of studies comparing low-fat/high-carb diets to low-carb/high fat diets published in the European Journal of Clinical Nutrition in 2022 found that both diets were effective for weight control and reducing cardiovascular risk factors, but concluded that further studies with long-term follow up were needed to confirm these findings. A separate 2022 systematic review published in the Cochrane Database of Systematic Reviews similarly concluded that there was "probably little to no difference in weight reduction and changes in cardiovascular risk factors up to two years' follow up, when overweight and obese participants without and with [type 2 diabetes mellitus] are randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets."

The Mediterranean diet, which is relatively high in fiber and monounsaturated fats (such as olive oil) has also attracted the attention of nutrition researchers. Some evidence suggests that it is as effective as low-carb diets for weight reduction, and probably more effective than low-fat diets. It also seems to have the added advantage of benefiting persons with diabetes more than the other two diets.

Very low carbohydrate diets, called ketogenic diets, have become popular for weight loss. These diets are extremely low in carbohydrates, modest in protein, and high in fat. They require dieters to get 75 percent of their calories from fat, 5 percent, or 20 to 50 grams per day, of calories come from carbohydrates, and 15 percent come from protein. People following these diets eat foods such as fatty fish, eggs, dairy, oils, butter, meat, and low carbohydrate vegetables. While people on these diets often lose weight quickly, they are at risk for problems such as kidney stones, low blood pressure, constipation, and increased risk of heart disease. People who take medications for diabetes should not try to lose weight on a ketogenic diet. Studies have also shown that these diets are dangerous in the long term, putting individuals at risk of developing cancer, diabetes, kidney failure, and Alzheimer's disease.

Most health experts suggest that dieting according to fads overall is ineffective, as any immediate weight loss is typically not sustained long term. Instead, most recommend that following a balanced diet in combination with regular exercise and other healthy habits is the best way to manage weight and promote overall well-being.

Risks

Any form of extreme dieting can cause serious side effects or even death. All people who intend to adopt an unconventional diet should first seek medical advice. Furthermore, people with kidney failure should not use low-carb, high-protein diets, as high-protein intake can easily overstress failing kidneys. (High-protein diets are probably not harmful for people with healthy kidneys.)

In addition, people who take the blood thinner warfarin (Coumadin) may need to have their blood coagulation tested after beginning a high-protein, low-carb diet. Two case reports suggest that such diets may decrease the effectiveness of warfarin, requiring a higher dose. Conversely, a person who is already on warfarin and a high-protein, low-carb diet and then goes off the diet, may need to reduce their warfarin dose.

The long-term effects and safety of low-carbohydrate diets, like other fad diets, are largely unknown. This is in part due to a lack of reliable and significant studies on the subject, though research is ongoing. However, the popularity of weight-loss diets means that even small studies making positive or negative claims about long-term effects are often highly publicized. For example, a study published in The Lancet in 2018 made headlines for linking both low-carb and high-carb diets with a higher risk of early mortality. Many critics of low-carb diets cited this as proof of such diets' flaws, but proponents of low-carb diets noted the study was purely observational and therefore did not prove any cause and effect. It was also pointed out that the higher mortality risk was seen in those who primarily replace carbohydrates with animal proteins rather than plant proteins.

Bibliography

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