For years people relied on the energy balance equation to help themselves lose weight. Since a pound of fat contains 3500 calories, all you need to do to lose a pound of fat is burn 3500 more calories than you eat. Sounds simple enough, the problem is that this isn't how it works. While the calorie surplus or deficit that you create likely has some relationship to how much weight you lose, we don't know how strong that relationship is or how strongly other factors impact this number. In this blog I will go over the primary reasons why this approach should be abandoned.
1)To lose a pound of fat you need to burn far more than 3500 calories.
While a pound of fat does contain 3500 calories, you never burn 100% of your fuel from fat. In fact, under ideal conditions, you only burn 60% of your calories from fat. The kicker here is that ideal conditions involve walking, not running. So when you up the intensity from walking to running, you actually start burning more sugar as a percentage of total calories. Since you are burning more calories by running, this means that you are likely burning more total fat calories while running but it is at a lower percentage. So when you walk, you need to burn 5833 calories to lose a pound of fat and when you run this number increases. For a person who weighs 160lbs, this means they would need to walk 58.3 miles to burn 1 pound of fat, more than 2 marathons. If you held the same fat burning efficiency for running, you would need to run 1.84 marathons to burn a pound of fat.
2)The body adapts to energy expenditure/intake
It is a well known phenomenon that a person's resting metabolic rate, the amount of calories they burn during rest, drops when a person restricts calories. In a study conducted in 2007, researchers found this phenomenon to hold true and also found that physical activity also decreased in people undergoing calorie restriction(
1). Another well known phenomenon is that a person who has never run a mile before will burn more calories running that mile the first time than they will once they've been running a mile for a couple of months. Calories burned is not a static number and is completely different from person to person and even within the same person after they've been exercising or dieting for a period of time.
3)Nutrient/Energy extraction from bacteria
Another problem that mucks with the inputs of the energy balance equation is that bacteria found within your digestive tract alter the amount of nutrients and energy you absorb from your food. It's obvious that absorbing more energy from your food will throw your calculations off, but not absorbing the proper nutrients from food that power fat burning pathways can prevent fat loss and lead to nutrient deficiencies over time.
4)Hormones matter and a calorie isn't a calories, strictly speaking
Systems within the body communicate with one another via hormones. In order to burn fat efficiently it's important to have proper hormonal signaling within the body since fat can only enter fat burning pathways. If all calories were created equal, they would all be able to enter any energy pathway to provide fuel just fine, this isn't the case. To burn fat, fat burning pathways have to be signaled by hormones to ramp up, and 2 hormones that have a significant impact on fat loss are leptin and insulin. Leptin is a hormone that is secreted by fat cells and is important to appetite regulation, regulation of energy expenditure, and regulation of fat stores. Having chronically high levels of leptin leads to leptin resistance, meaning the body doesn't receive the signal properly and appetite and fat storage aren't regulated properly. Insulin regulates the storage of fat and helps select which fuel you use. When insulin levels are high, the body stops burning fat because insulin signals the body to store it. In insulin resistance, this signal is not received so the pancreas pumps out more insulin, preventing the use of fat for energy. It is believed that leptin resistance precedes insulin resistance which can eventually lead to Type 2 diabetes, a reversible metabolic state that can be ameliorated through diet and lifestyle modification. Just attending to calories in and calories out doesn't take errors in hormone signaling in to consideration.
5)Diet induced inflammation
Many people are familiar with inflammation as it pertains to cuts, bruises, and injuries. Inflammation is initiated by the innate immune system and is used to help clear pathogens from the body and begin the healing process. Dietary inflammation can occur due to overeating or from eating foods that inflame the digestive tract. High levels of leptin are known to activate the immune system(
2) and this is likely the mechanisms by which overeating increases inflammation. For foods that inflame the digestive tract, gluten is a known cause of inflammation for all people and other foods can be a cause of GI tract inflammation in some people but not others. In general, a small amount of acute inflammation is not seen as something an otherwise healthy person should worry about, it's when the inflammation becomes chronic that troubles arrive. High levels of certain inflammatory markers induce insulin resistance in muscle and fat tissue, sparing glucose so that the immune system can use the glucose to ramp up defenses. This causes blood glucose levels to rise and insulin levels to rise as well. A breakdown of this can be found in this
blog.
Conclusion
The calories in vs calories out approach to weight loss has taken an inordinate amount of time to die. The approach doesn't work, the inputs to the equation are dynamic and, thus, constantly changing, and the human machine is far more complex than a car that burns gas. If fat loss is an important goal of yours you should drop the calorie counters, ignore the calorie burn on your treadmill, and improve the way your "machine" works by paying attention to what it needs. This includes good quality sleep, stress management, daily physical activity, a nutrient dense diet with at least 6-9 cups of vegetables per day, and weekly vigorous activity.
