As a personal trainer, I come across a lot of people who want to lose weight. They work out like crazy and eat as little as possible. When they suddenly stop losing weight, they get confused, frustrated, and demotivated. And usually they don’t believe me when I tell them they could continue to lose weight if they only ate more.
Why people undereat
It seems simple enough. Eat less. Do more. Maintain a calorie deficit, and lose weight. This works well, but at some point (usually 5 - 15 lbs from their goal weight), just about everyone gets stuck.
When this happens, the panic sets in. We eat even less and do even more. Entire food groups are banned from the kitchen and we pile on hours upon hours of cardio. At this point, the logic behind calories in/calories out becomes our own worst enemy.
The effects of undereating
The body is pretty amazing; it continuously adapts to almost anything we put it through, and calorie restriction is no exception. Sustaining a constant calorie deficit teaches our bodies to run efficiently on fewer calories. Our resting metabolic rate (RMR) slows down to match the intake and boom, we hit a wall. This is where so many diet plans fail.
When we undereat, our bodies go searching for internal fuel to burn. Sure, we might torch some fat, but your body will also go after lean muscle. This is unfortunate because muscle burns more calories than fat (every 10 lb of muscle burns about 50 calories a day while resting, versus fat’s 20 calories). Therefore, when we hit that weight loss plateau the best response is to focus on creating more muscle.
Shift your mindset: Food is fuel
Thinking of food as the enemy and as the thing that is stopping you from losing weight is counterproductive. Your body needs fuel - and in particular, protein - to maintain and build lean mass. The government’s Recommended Dietary Allowance (RDA) stipulates that your daily protein intake should equal .36 grams of protein per pound of body weight. In the fitness community, you'll hear a different story; recommendations of as much as 0.75 - 1 gram of protein per pound of body weight are common. For someone who is 160 lbs, that's 120 - 160 grams of protein per day.
But building muscle requires more than just eating protein. Resistance training is what stimulates muscle growth. In order to lift weights, your muscles need easily accessible energy, and that energy comes from carbohydrates. Fats are equally essential for good health and the ability of your body to absorb certain vitamins and minerals. Therefore: eat all the foods. Contrary to the latest diet fads, carbs are not evil, and neither are fats. Food is fuel. Every body is different so you have to pay attention to how your body responds to what and when you eat. Weight loss is never linear, nor should it be.