It is NOT necessary to eat less carbs to lose weight.
Weight loss occurs when you burn more calories than you take in. The body can take calories from the following food sources:
- Fat: 1 gram = 9 calories
- Protein: 1 gram = 4 calories
- Carbohydrates: 1 gram = 4 calories
- Alcohol: 1 gram = 7 calories
It can also break down body fat and muscle when there's no more food in your gastrointestinal tract. The rate at which this occurs is not as simple as counting grams of food, so I won't go there.
The body uses those calories for maintaining these functions:
- 5% - building muscle
- 20% - exercise
- 25% - brain
- 50% - basal metabolism
As long as the sum of all the grams of food you eat multiplied by their respective caloric value is less than the calories you expend, weight loss will occur. Take this oversimplified example of a typical day: I eat 50g of carbs and 10g of fat. And lets say I sat in some scientific chamber to measure heat generated by calorie usage and determined that I expended 300 calories.
CaloriesIn = 50 * 4 + 10 * 9 = 290
CaloriesExpended = 300
Net = 290 - 300 = -10
Where can the body get this 10 calories it needs to survive? My food has been depleted, so I'll go into my blubber to burn those 10 calories. And there you have it: body fat is lost.
Now let's say you wanted to go on a low carb diet. Since I'm not eating my pasta and bread, I'm going to satiate my stomach with extra fat. In this example, I will eat 30g of fat and 5g of carbs. I will also carry out my day as usual by expending 300 calories.
CaloriesIn = 5 * 4 + 30 * 9 = 290
CaloresExpended = 300
Net = 290 - 300 = -10
I still have a negative net value, meaning I will lose weight. You see, no matter if it's a low or high carb diet, it is still possible to lose weight.
Why do we hear about these low carb diets like the Atkins diet? It's just a matter of preference. People on low carb diets may not like eating bread, pasta, and rice. They much rather eat fats like cake, fatty meats, and ice-cream. All they've done is shifted the caloric intake from carbs to fats. There's no magic here.
Another reason for sticking to low carb diets is because fat is very hard to burn. If fat from your food is not burned, it will be deposited as body fat. During cardiovascular exercise, the body more readily burns carbs. It burns very little food fat. As the cardio progresses, the ratio energy consumption shifts towards fat. After an hour of steady cardio, the ratio of carb to fat usage can be as much as 50:50. Thus, people who don't have time to do hours of cardio should eat less carbs. Well, you should eat less of everything in general, but the proportion of carbs should be lower. This way, the body will be forced to burn the food fat as soon as whatever little amount of carbs you have is depleted.