Severe carbohydrate restriction can cause the body to break down fat into ketones for energy, resulting in ketosis. This can lead to side effects such as bad breath, headache, fatigue, and weakness. It's unclear what kind of potential long-term health risks a low-carb diet can pose. In addition, low-carb diets lead to a drastic reduction in insulin levels, causing the kidneys to eliminate excess sodium and water.
For example, 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. What is the final result? 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's 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. The resurgence of low-carb diets has led many people in the general public to wonder if carbohydrates are inherently “bad” and should be limited in the diet. However, 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. 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).
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. 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. The reason why quitting carbohydrates can be so effective for losing weight is because people tend to eat the wrong types of carbohydrates. Low-carb ketogenic diets have no metabolic advantage over non-ketogenic low-carb diets. Perhaps the biggest problem with eliminating carbohydrates completely on a low-carb diet is that it is not sustainable in the long term. And, of course, rT3 increased on the low-carb diet, but not on the standard or high-carb diets.
Extensive study concludes that low carbohydrate intake increases risk of premature mortality, as well as mortality from several chronic diseases. Studies examining the effectiveness of using low-carb diets for long-term weight loss are few, yet there are few positive benefits to promoting the adoption of carbohydrate restriction as a realistic and safe means of dieting. Many studies show that low-carb diets are good for physical performance, especially endurance exercise, as long as you give yourself a few weeks to adjust to your diet. In addition, 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. In conclusion, while the low-carb movement has increased and decreased in popularity since the Atkins revival in the late 90s and early 2000s, most people now assume that carbohydrates are inherently fattening. However, evidence suggests that there are no significant advantages to following a low carb diet over more traditional diets with energy restrictions and nutritionally balanced meals.