Popular diets emphasizing low-carbohydrate intake are controversial partly because

They have limited evidence about the long term consequences, health risks and side effects

There is still limited study on the effects of having low carbohydrates diet. Evidence are not enough to guarantee the safety and efficacy of this type of diet specially in losing weight. The effect of having low carbohydrates in the diet can lead to decrease output of the thyroid, increased input on cortisol, impaired mood and cognitive function, muscle catabolism, suppressed immune function.