What happens if you don't eat enough calories?

If you aren't getting enough calories per day, you will lose weight. However, the weight you lose is not the kind of weight you want to be losing.

There are two sources of weight in our bodies: fat weight, and lean weight.

Fat weight is fat,

Lean weight is muscle, bone, organs and connective tissue like ligaments and tendons. 

Toning up your body requires losing FAT, and to lose FAT, you must eat enough nutrient-packed calories for your metabolism (your body's calorie burning mechanism) to function properly. To figure out that number, estimate it here.

Calorie restriction causes your body to go into starvation mode where, panicked because its not getting what it needs, your body stores and hangs on to every last ounce of fat you have, and for energy, it burns up your lean mass. Bone density decreases with calorie restriction (so you are more susceptible to break a bone) and so does the strength of your connective tissue (hellooo, sprained ankles). Maybe even more importantly, you're losing muscle mass, so you end up looking like a squishy, shape-less weak mess, and that's not attractive.

To make it even worse, calorie restriction screws with your metabolism, making it harder to lose fat in the long run. 

On the flip side, building muscle raises your metabolism, meaning your body needs more calories per day to be healthy (which is awesome, because then you can eat more.)

If you're a serial weigh-er, know this: Lean muscle weighs more than fat, so if the scale doesn't fluctuate too much, don't freak out. You're losing fat and building heavy, lean muscle.

How do you avoid becoming skinny-fat like that guy up there? Eat your daily recommended amount of calories, and make sure they're coming from whole, nutritious foods... AND, lift weights. Muscle doesn't appear out of nowhere.  

Eating is good. Eat. Don't starve yourself. Don't be skinny fat.