A person can become obese even on a fat-free diet explain?

Answer 1

The human body is a master of storing energy and using it efficiently. Other sources of calories/energy are used up as fuel to move and for bodily functions (breathing, heartbeat, etc.)

Now, any kind of energy can be stored as fat due to a special cell organelle that does this for us.

Assume you need 2000 calories a day to maintain your weight. Now, if you ate 3500 calories on top of that (so 5500 calories) you would gain about a pound of fat. Now, let's say you eat 5500 calories a day for your whole life. Let's also say that 500 of those calories come from protein, 4900 come from carbs, and 100 from sugar. You'd gain a pound a day, and be obese in less than a year. But you won't have eaten any fats!

Dietary fat (fat that you eat) is about twice as fattening than other types of calories. However, it is also good for you to get a portion of your calories per day from healthy fat (i.e. regular, polyunsaturated, or monounsaturated fat). Trans and saturated fats are very bad for your health.