Severe carbohydrate restriction can cause the body to break down fat into ketones for energy, leading to ketosis. This can cause side effects such as bad breath, headache, fatigue, and weakness. It is unclear what kind of potential long-term health risks a low-carb diet can pose. Additionally, low-carb diets lead to a drastic reduction in insulin levels, causing the kidneys to eliminate excess sodium and water.
A 6-week study of low-carb diets showed that participants lost 7.5 pounds (3.4 kg) of fat, but gained 2.4 pounds (1.1 kg) of muscle. Low-carb diets also tend to be high in protein, which stimulates metabolism and causes a slight increase in the amount of calories burned. Other studies indicate that low-carb diets benefit muscle mass and strength. However, not eating enough carbohydrates can lower T3 levels, alter cortisol-to-testosterone ratios, interfere with a woman's delicate hormonal balance, contribute to muscle loss, and prevent muscle mass gain.
It is perfectly healthy to follow a low-carb diet, as long as it includes a variety of nutritious, whole grain, and unprocessed foods. Low-carb diets can be good for heart health, as they can increase good cholesterol levels and lower blood pressure and triglyceride levels. In one study, subjects who ate a moderate-carbohydrate diet (40% calories from carbohydrates) reported significantly better mood and lost approximately the same amount of weight as those on a low-carb ketogenic diet (5% of calories from carbohydrates). In another study in Life Sciences, men who ate a high-carb diet compared to a low-carb diet for 10 days had higher levels of testosterone and sex hormone-binding globulin, and lower levels of cortisol.
Low-carb ketogenic diets have no metabolic advantage over non-ketogenic low-carb diets. Studies show that some people successfully lose weight on a low-carb diet, just as they do on a low-fat or Mediterranean-style diet. In fact, the group that consumed a moderate amount of carbohydrates showed a small (though not statistically significant) tendency to lose more body fat compared to those who followed a low-carb diet (5.5 kg vs 3.4 kg in 6 weeks). Evidence abounds that low-carb diets do not present a significant advantage over more traditional diets with energy restrictions and nutritionally balanced, both in terms of weight loss and weight maintenance. The biggest problem with eliminating carbohydrates completely on a low-carb diet is that it is not sustainable in the long term.
Low carbs keep insulin low, which should make you lose weight effortlessly while enjoying chicken wings, salmon, eggs and butter. However, in one study the low-carb diet increased muscle breakdown because very low carbohydrates lowered insulin levels. And rT3 increased on the low-carb diet but not on the standard or high-carb diets. In addition, low-carb users were 51 percent more likely to die from coronary heart disease, 50 percent more likely to die from cerebrovascular disease, and 35 percent more likely to die from cancer. Even in athlete trials where the vast majority of participants perform better on high-carb diets than low-carb diets you'll almost always find some who perform better on a low-carb diet. Especially considering that a recent review of long-term low-carb versus low-fat diets found that both low-carb and low-fat diets reduced people's weight and improved their metabolic risk factors. Overall, it is important to remember that while following a low carb diet may help you lose weight in the short term it is not sustainable in the long term and may even be detrimental to your health.
