1. Daily Calorie Needs

Know Your Requirements   

Okay, this isn’t technically a measurement, but it’s a number that, if you pay attention to it, can have a huge influence on your health.

How much food should you eat in a day? Few people know the answer to this question. Here's a basic formula for calculating your calorie needs: from 13 to 15 calories per pound of body weight per day, depending on your activity level.

How much food do you actually eat? Many of us nibble and nosh our way through the day without any real sense of how much we’re consuming. In most cases, we are eating much more food than we need.

In a perfect world, the difference between your daily intake and your daily needs would be zero—that is, you’d eat just enough to provide fuel for your body. If you were trying to lose weight safely, you’d eat roughly 500 calories less than your body requires. The reality is, though, that many of us eat from 100 to 1,000 calories more than we need.

It sounds simple, but no health number is as important—and as instructive—as the one that helps you understand your daily food needs and whether you’re exceeding them. The obvious reason is that overeating leads to weight gain, and becoming overweight is among the worst things you can do for your heart and health. The less-than-obvious reason is that eating too many calories usually means eating unhealthy foods, since they’re so much higher in calories than natural, healthy foods because of all the fat and sugar in them. It’s almost impossible to get too many calories if you focus on eating lots of fruits and vegetables. And having a diet rich in produce means you get loads of vitamins, minerals, antioxidants, and other nutrients essential for heart health.

Most women need approximately 1,800 calories a day for good health. Men typically need about 2,100. That usually equates to 300 to 400 calories for breakfast, 400 to 500 for lunch, 500 to 600 for dinner, and two or three snacks of roughly 100 to 200 calories each.

But don’t rely on such broad estimates. Your daily calorie need isn’t a static number; it can change over time. If you are exercising more, healing from disease, or in a high-stress period, your body may need extra fuel. If you’ve lost weight, chances are your body requires less fuel than it once did. Then there’s metabolism—some of us burn calories more efficiently than others.

The main message: All adults should have a good understanding of how much food they need to eat each day for optimal health, energy, and weight. The trick is how to do that. Calories are the simplest statistical measure, but steak doesn’t have its calorie count stamped on it anywhere, and who wants to look up everything they eat in a calorie counter and keep a tally of it all? The next best way—and the one we recommend—is visual training: learning what, for example, a 300-calorie breakfast looks like.