If you’ve ever tried to lose weight, there’s a good chance you’ve been told that it all boils down to a simple “calories in, calories out” formula: Burn more calories than you consume, and the pounds will disappear.
And it’s easy to see the appeal of breaking down weight loss into simple calculations, just follow the formula and you will achieve success. It’s also believable because many people lose weight when they first take this approach.
In fact, the diet industry’s reliance on the concept of “calories in, calories out” is why society blames people for being overweight. Anyone who fails to follow this simple energy formula is overweight only because they lack the willpower to eat less and exercise more.
But the one simple truth here is that it’s time to dispel the myth of “calories in, calories out” as the only way to lose weight. Here because.
It is nearly impossible to calculate accurately
The many calorie-counting apps and online calculators available make it look easy. Simply enter your gender, age, height, weight, body composition, and activity levels, and they’ll tell you exactly how many calories you should be eating each day to lose weight.
Unfortunately, no matter how accurate these calculators claim to be, they are based on averages and cannot determine the appropriate calorie intake for you with 100% accuracy. They can only estimate.
Similarly, our metabolic rate, the amount of energy we burn at rest, also varies from person to person based on many factors, including body composition or the amount of muscle and fat we have. To complicate matters further, our metabolic rate also alters when we change our diets and lose weight.
Calculating calories in food, the other part of managing “calories in,” is also far from accurate.
Although Australian food standards require food products to display nutrition information panels showing energy in kilojoules, there are no requirements for the information to be accurate other than that it must not be misleading. A worrying discrepancy of +/-20% is generally accepted for labeled values.
In practice, the variation can be much more. An Australian study found that food contained between 13% less and 61% more energy or nutrient components than stated on the packaging.
Not all calories are created or consumed equally
Another reason the simple “calories in, calories out” formula isn’t so straightforward is that our bodies don’t consume all calories equally. What is showing in your calorie counter is not what is actually being absorbed by your body.
Different calorie sources also have different effects on our hormones, brain response and energy expenditure, changing the way we respond to and manage our food intake.
For example, while eating 180 calories of nuts is the same as eating 180 calories of pizza in terms of energy intake, how these foods are absorbed and how they affect the body is very different.
While we absorb most of the calories in a slice of pizza, we don’t absorb about 20 percent of the calories in nuts because their fat is stored in the nut’s fibrous cell walls, which don’t break down during digestion. Nuts are also rich in fiber which fills us up for longer, while a slice of pizza prompts us to grab another right away thanks to its low fiber content.
Our bodies disrupt the formula
The biggest failure of the “calories in, calories out” formula is that it ignores that the body adjusts its control systems when calorie intake is reduced. So while the formula may help people initially achieve weight loss, the reduction in energy intake is counteracted by mechanisms that ensure that the lost weight is regained.
That is to say, when your body experiences a sustained decrease in the calories you consume, it believes its survival is threatened. It then automatically triggers a series of physiological responses to protect itself from the threat, reducing our metabolic rate and burning less energy.
This stems from our hunter-gatherer ancestors, whose bodies evolved this response to adapt to times of deprivation when food was scarce to protect against starvation.
Research also suggests that our bodies have a “target weight”—a genetically predetermined weight that our bodies try to maintain regardless of what we eat or how much we exercise.
Our bodies protect our set point as we lose weight by managing biological signals from the brain and hormones to hold onto fat stores in preparation for future reductions in our calorie intake.
The body achieves this in several ways, each of which directly affects the “calories in, calories out” equation, including:
slowing down our metabolism. When we reduce our calorie intake to lose weight, we lose muscle and fat. This decrease in body mass results in an expected decrease in metabolic rate, but there is an additional 15% decrease in metabolism beyond what can be explained, further disrupting the “calories in, calories out” equation. Even after regaining the lost weight our metabolism does not recover. Our thyroid gland also malfunctions when we limit food intake and less hormones are secreted, also changing the equation by reducing the energy we burn at rest
by adapting the way our energy sources are used. When we reduce our energy intake and begin to lose weight, our body switches from using fat as an energy source to carbohydrates and retains its own fat, resulting in less energy being burned at rest
manage the functioning of our adrenal gland. Our adrenal gland manages the hormone cortisol, which it releases when something that stresses the body such as calorie restriction is imposed. The excessive production of cortisol and its presence in our blood changes the way our body processes, stores and burns fat.
Our bodies also cleverly trigger responses to increase our caloric intake to regain lost weight, including:
regulating our appetite hormones. When we reduce our calorie intake and deprive our bodies of food, our hormones work differently, suppressing feelings of fullness and telling us to eat more.
changing the way our brain works. When our calorie intake is reduced, the activity in our hypothalamus, the part of the brain that regulates emotions and food intake, also decreases, decreasing our control and judgment over our food choices.
The “calories in, calories out” formula for weight loss success is a myth because it oversimplifies the complex process of calculating energy intake and expenditure. More importantly, it does not take into account the mechanisms that our body activates to counteract a reduction in energy intake.
So while you may achieve some short-term weight loss by following the formula, you will likely gain it back.
Additionally, calorie counting can do more harm than good, taking away from the pleasure of eating and contributing to developing an unhealthy relationship with food. This can make it even more difficult to achieve and maintain a healthy weight.
For long-term weight loss, it’s important to follow evidence-based programs from health care professionals and make gradual changes to your lifestyle to ensure you form lifelong habits.
At the Boden Group, Charles Perkins Center, we are studying the science of obesity and conducting clinical trials for weight loss. You can register for free here to express your interest.
Nick Fuller, head of the research program at the Charles Perkins Center, University of Sydney
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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