Want to lose weight? Eat less. Exercise more.
That is the answer you might get from your well-meaning co-worker, popular magazines, and maybe even your family doctor. It seems logical. If you eat less your body has less to get rid of, right? Unfortunately, weight loss is a little more complicated than this.
Calories. What are they?
A calorie is defined as the amount of heat energy needed to raise the temperature of one gram of water by 1 °C. More commonly, a calorie is known as a means used to measure the amount of energy your body gets from foods and drinks.
Calories are used for three purposes. First, a certain number are needed for basic bodily function at rest, like breathing, blood circulation, etc. This amount varies by person depending on height, weight, age, and gender. This is known as your basal metabolic rate (BMR). Calories are also needed to digest the foods and drinks that are consumed. This is known as the thermic effect of food (TEF). Finally, calories are needed to supply the body with enough energy to complete daily activities such walking, cleaning, exercising, etc.
Feel the burn.
You might be familiar with the “calories in vs calories out” model. This concept implies that to maintain your weight you must balance the number of calories consumed (calories in) by the number of calories that you burn (calories out). It also implies that to lose weight you must consume fewer calories than your body uses. Hence the eat less and exercise more advice.
This stems from the fact that if you consume more calories than your body needs the remainder will be stored for future use, mostly as fat (1). Eating fewer calories leads to weight loss, except for when it doesn’t.
Caloric deficit. When too few is too much.
By eating fewer calories than your body needs you will be putting yourself in a caloric deficit. A deficit leads to weight loss as your body will burn more than is being used. Unfortunately, many people assume more is better. They begin to drastically cut calories in attempts to lose more weight. Not only is this counterproductive, it is also harmful to their health.
When you eat fewer calories than needed for daily functioning, your body switches to survival mode. This countermeasure causes your metabolism to slow down so your body can conserve energy. This can decrease your body’s caloric burn by more than 20% (2,3,4).
This process can also increase cravings and make you feel hungrier. If you continue to eat in this drastic caloric deficit your body will start to eat muscle tissue for energy further decreasing your metabolism.
As it turns out, your brain has more control over your weight than you may think. Research has found neurons in the brain that determine whether our bodies go into calorie burning mode or calorie saving mode (5). These neurons coordinate appetite and energy expenditure (caloric burn). Depending on your genes and life experience, they help to set a weight range that your body wants to stay in. This makes it more difficult for your body to lose weight. The more restrictive dieting you participate in the more opportunities you are giving your body to reset this weight range to a higher point. It is all a part of the survival process.
The Goldilocks phenomenon.
If weight loss is at the mercy of your brain and metabolism, how do you get in control? You need to make sure you are eating enough calories to get your body out of survival mode.
First- determine your BMR- use an online calculator, like this one, to determine the minimum amount of calories your body needs for proper functioning at rest (this does not include daily activities or exercise).
Next, estimate your daily caloric need- use another calculator, like this one, to determine the number of calories you need to stay at the weight you are at.
Finally, determine your caloric need for weight loss- aim for a daily goal that falls between
these two estimations. A healthy caloric deficit is usually 300-500 calories below your daily caloric need.
More than just calories.
If weight loss is your goal, you need to eat fewer calories than you burn. The more complex side to this is not all calories are created equal. Different foods have different effects on your body and how those calories are digested.
Different foods can affect your hormones in different ways. One example is fructose. Consuming foods rich in added fructose is linked to insulin resistance, increased blood sugar levels and higher triglyceride and LDL (bad) cholesterol levels. Consuming fruit, which contains natural fructose, fiber, and water, does not have the same negative effects (6,7,8).
Different foods can affect your hunger in different ways. Foods that are rich in protein or fiber are more filling than foods that are less nutrient dense. This means eating 100 calories of beans is going to reduce your hunger more than eating 100 calories of M&M’s. The M&M’s are also going to cause your blood sugar to spike then drop leaving you hungrier and more apt to overeating.
Different foods can affect your metabolism in different ways. Certain foods require more energy to digest or absorb than others. These foods have a higher TEF. Protein has the highest TEF while fat has the lowest. That means you burn more calories digesting protein than fat.
In the end.
There is more to losing weight than eating less and exercising more. You must tune-in to your body and discover the Goldilocks effect for the right number of calories your body needs. Learning how to use the “calories in vs calories out” model effectively has its advantages, but it certainly isn’t the whole picture. Making the right food choices is just as important for health as it is for weight loss.