Contrary to popular belief, it is not the types of nutrients (carbohydrate/fat/protein) that you eat that leads to weight gain. It is simply the quantity. Carbohydrates won’t make you any fatter than if you ate the same amount of calories in protein or fat. In fact, fat won’t even make you fat if you consume fewer calories than you expend. You may be surprised to know that all types of foods (carbohydrate/fat/protein) are broken down to the same basic compound for energy production. All nutrient roads lead to ATP (your body's gasoline) regardless of the form in which they start.
Everyone knows that food provides energy. A food’s energy is measured in calories. A calorie is simply a way to quantify how much energy is present in a food. The problem is that your body cannot use food for energy in its primary state. In other words, you cannot simply press a hamburger up against your thigh and expect it to give your leg energy. Even more specifically, your body cannot directly utilize fat, carbohydrate, or protein as a source of energy. All these nutrients need to be broken down into an energy form that the body can utilize.
The body’s process of converting food into an energy source is similar to oil being converted into gasoline. Crude oil must be processed in a factory and turned into gasoline before it will be of any use to you and your vehicle. You could try skipping the processing step and simply put crude oil directly in your gas tank. But, as you know, this will not provide you with any utilizable fuel source. Your car will not run. Gasoline is what you need.
So how does your body take nutrients such as carbohydrate, protein, and fat and convert it into “gasoline” for your cells? Inside every cell in your body there is a process that takes place referred to as the Krebs cycle. The Krebs cycle is simply the conversion of nutrients into a universal energy form called ATP. ATP is the energy that your body utilizes to perform tasks. This is the end result of carbohydrate/fat/protein digestion. It does not matter what nutrients the body starts with, regarding food. If food is needed for energy, it will be converted into ATP.
To simplify your understanding, imagine a hamburger. A hamburger has carbohydrate in the form of the bun, protein in the form of meat, and fat in the form of meat and mayonnaise. First, the hamburger will be digested into its component parts – fat/carbohydrate/protein in the stomach. These nutrients will then be absorbed by the body in the intestines. The intestines will then transfer the nutrients to the bloodstream. The bloodstream will then carry the nutrients to the individual cells. Unfortunately, in their forms as fat carbohydrate and protein, these nutrients are not utilizable by the cell for energy. They will need to take a trip through the Krebs cycle. This will convert the nutrients into energy or ATP It matters not how they started, all types of foods end their journey as ATP.
With this in mind, you can see that it's not one particular type of food would makes you fat. Since all nutrients end up as the same end product, you can see that it is much more important to be mindful of the amount of food you consume as opposed to the type.