The reason why is simple, carbohdrates are fuel. Everyone is carbohydrate sensitive if you are taking in more fuel than you use. Carbohyrate holds water, for activity!
If weight loss is your goal, then controlling carbohydrates is a great way to go, but then understand activity is not naturally promoted when you eat a low carb diet.
Studies completed in The China Study – the most comprehensive study of nutrition ever conducted, show that animals eating a carbohydrate rich diet from the right sources, are naturally more active than those fed a more animal protein centric diet.
A good question, is what you do mean when you say controlling carbs?
The key distinctions are in fact real food vs fake food, and the foods that give you the right level of carbohyrate to serve your needs; based on activity levels.
If you are eating carbohydrates from the right sources and based on activity levels, activity will be naturally promoted and you won’t store so much excess fuel!
Learn more about this in Losing Weight the Nutrient Rich Way.