Exercising more does not get you skinnier. Not by a lot anyway because evolution has primed us to burn only that many calories in a day, regardless of our lifestyle, says Dr Herman Pontzer, an evolutionary biologist from Duke University. It’s what he discovered in his fieldwork with the hunter-gatherer Hadza tribe in Northern Tanzania. Despite being more physically active (their daily step-count alone is about 13,000 steps), a Hadzabe burns the same number of calories as the average urbanite in the West – about 3,000 calories daily.
This new data is also chronicled in his book, Burn: New Research Blows the Lid Off How We Really Burn Calories, Lose Weight and Stay Healthy. It reframes the way we look at metabolism and makes it clearer how “diet and exercise are two different tools for two different jobs.” The former is the tool for weight loss, while exercise is “your tool for everything else.”
All of us have the same energy budget
Metabolism, says Dr Pontzer, is simply the umbrella term for all the work that your cells do, using energy.
All of us have the same energy budget based on body weight, but our bodies decide where it will allocate that resource. We spend some on physical tasks like moving or exercise, although that only accounts for less than half of the budget. The rest is utilised by unseen tasks that the body performs. Our brain, for example, burns off about 300 calories each day, telling our bodies what to do.
The Hadza expend more energy on physical activity, but their bodies compensate for that by devoting less of it elsewhere, such as fighting inflammation or on stress responses. This auto-compensation is evolution at work, when the body adapts to a lifestyle to stay within a narrow calorie burning band (for energy).
Survival instincts
Incidentally, evolution is also behind our propensity for weight gain. We are fat primates, with anywhere between 14 to 31 per cent of body fat; other apes have less than nine per cent. Fat helps us store energy and protects our vital organs. But there’s also our hungry, bigger brains. Pound for pound, the brain uses up more energy than any other tissue. Plumping up, hence, would have given early humans added fuel for brain development.
That’s all good if you are trying to survive harsh, famine conditions, not so for weight loss. Your body only has one goal: Not dying. Hence it does everything to stick to plan, thwarting your best weight-loss efforts.
Image Credit: fizkes/iStock/GettyImages
The struggle is real
Yes, you may burn more calories if you run a marathon tomorrow. Or see some weight shifting when you start working out. But over time, the body adapts to the new changes and cleverly manipulates metabolism to return to status quo.
Functional health expert, Dr Julinda Lee explains: “When the body burns more energy during exercise, it is concerned that there will not be more food coming. Hence it compensates by reducing the number of calories burned at rest.”
Similarly, when you drastically cut calories, the body will conserve energy by reducing activity elsewhere. Subsequently, you may feel sluggish and cold.
Familiarity is another reason why you have hit a weight-loss plateau. “When your body becomes used to your exercise routine, you may burn fewer calories,” she says.
Body composition also influences calorie burn since fat burns fewer calories than muscle. As women tend to have more body fat, this puts us at a slight disadvantage. (Dr Pontzer says the average woman burns about 2,400 calories daily)
Since it is hard to change how many calories we burn, and more exercise ends up being counter-intuitive for weight loss, we need to look harder at the calories we consume.
You are what you eat
“Most people who gain weight do not have a hormonal problem that is considered disease,” says Dr Lee. The excess weight is more likely from eating more calories (over time) than their bodies need. She says having a poor relationship with food – if you comfort eat; eat a highly-processed diet (read high in refined carbohydrates and saturated fat); or are a serial dieter – can potentially disrupt our energy balance and make it hard for the body to self-regulate.
To achieve weight loss, a calorie-deficit is necessary. However, “a slow and sustained reduction is important to ease the body into a state of calorie-deficit that does not result in stress.”
That is because dropping weight rapidly triggers “appetite-stimulating chemicals to be produced at high levels”. The stress coupled with these appetite-stimulating chemicals like ghrelin, and conversely reduced levels of leptin (our satiety hormone), can cause a voracious hunger and a compulsion with food that trips “our willpower to continue pushing ourselves through exercise and restricting calories.”
Most, she notes, will end up increasing the amount of food they eat, inevitably regaining the weight. Instead, a more measured strategy gives “the body and your hormones some time to regain balance, so that it can once again be receptive to a more sustained effort at weight-loss.”
She advocates eating whole, not processed foods. Vegetables especially, fill you up yet are low-calorie. It is also important you “understand why you eat, when you eat, and when you are likely to eat foods that you consider bad or unhealthy. Often, losing weight involves addressing other issues that are bothering us, such as our relationships or work.”
Getting adequate sleep and managing stress are also key, as both impact appetite-regulation. She says not only do we consume more calories when either are affected, we tend to crave refined sugars and saturated fat since they “have chemical properties that increase feel-good hormones or endorphins in our brain and is how we self-medicate.”
Can we quit the gym?
You can, but you must exercise, regardless. While exercise may not affect the scales greatly, it critically impacts our health. It makes you stronger, fitter, and helps to lower risks of many chronic diseases. A physically active person is one and a half times less likely to develop coronary disease; and 30 to 50 per cent less likely to be hypertensive. It also reduces the risk of Type 2 diabetes, many types of cancer, depression, anxiety, and dementia.
People who are active have greater life longevity. When obese men and women start exercising and improving their fitness, it lowers the risk of premature death by 30 percent or more, even without them losing the weight. They also fare better when compared to those who are not overweight but are unfit.
Exercise also improves your functional fitness, so you can walk, bend, lift and climb stairs, without pain, injury, or discomfort. You should be able to do these things well into your golden years, without great difficulty or compromised mobility.
“Focusing on BMI or weight alone may not be a fool proof way of determining health. But at any weight, a person who is physically active is more likely to be healthier compared to a person who is not physically active,” says Dr Lee.
