You know the math when it comes to losing weight: Eat smarter and exercise. What you don’t need is fad diets or get-thin-quick schemes. It’s all about data — and if you’re logging in MyFitnessPal, a little scientific knowledge helps you understand what’s going on inside you. That’s what we’re here to provide: a comprehensive look at what happens in your body when you’re looking to lose weight.

It all starts with calories, the basic unit in foods and beverages that provides your body with energy. All calories are the same: 150 calories from a cookie or Greek yogurt is still 150 units the body converts to energy. But how many you can handle is unique to your body: Your calorie budget depends on a variety of factors, including your physical-activity levels, muscle density and genetics. Now to the science …