Cutting calories on white background

by Jenny Gaal, Fitness Director


Sorry to break it to you—burning a pound of fat isn’t as simple as burning through 3,500 calories.

There’s tremendous variability in how a 3,500 caloric deficit affects different people.  Why’s that? Well, one huge factor determining the results of dieters is body composition.  The more fat a person has to give, the quicker she/he will lose weight and weight from fat.  Meanwhile, when you get closer to your body weight, your body holds on to fat stores for dear life and sacrifices muscle over fat because the body is perpetually afraid that it will starve; it’s perhaps biology’s most un-welcomed survival mechanism.

Meanwhile, how you try to hit your caloric deficit (which is a necessity to lose weight) has a huge impact on whether you lose weight from muscle, fat or just water.  The faster you try to achieve a deficit, the more weight you will lose from muscle as opposed to fat. However, exercise—and most markedly, strength training—and protein consumption promote muscle growth so that you will not lose as much muscle. In fact, if you consume an adequate amount of protein, you could potentially increase your lean-muscle mass while reducing your body-fat percentage.

Take it a step further, if you are cutting calories from carbs, you will also lose water weight. In the body, every gram of glycogen (carbohydrates) in your body is stored with a few grams of water. So when you go low-carb, your metabolism breaks down those glycogen reserves for energy, and you end up naturally flushing out the accompanying water. That’s another reason why, calorie per calorie, obese people tend to drop weight drastically: They have a lot of water to lose.

You also need to realize that your calorie-cutting strategy does alter your metabolism—and what it takes to take in fewer calories than you’re consuming over the long haul.  People’s metabolic rates slightly decrease as they lose weight. That’s because it takes more energy (calories) to fuel a 280-pound human than at 180-pounds.  More importantly, if you lose most of your weight from muscle, your metabolism will plummet—which is one more reason why extreme diets do not work.

The math is simple.  Aim to take in 300 to 500 fewer calories per day to lose weight and fit in a healthy exercise regimen.