For a long time, we believed that the best strategy for weight loss was restricting calories, keeping fat consumption low, and exercising. Over the last few years, scientists have made some incredible discoveries about the actual underlying causes of weight gain. It’s time to take full advantage of these new insights to solve our weight problems once and for all.
New insights have led to more effective strategies for sustainable weight loss
Insight #1: Restricting calories does not work in the long run
Going on a restrictive low-calorie diet does make you lose weight in the short run. The problem is that your body gets the signal that it’s starving. To protect you against starvation, your body will decrease its energy expenditure by lowering the body’s basal metabolic rate. At the same time, it makes you extra hungry in order to motivate you to get out there and fuel up. After a while, you had enough of feeling tired and hungry all the time and you slightly increase your calorie intake. Your weight will go up quickly because of the decreased energy expenditure and it may even end up higher than where you started. Your body will have moved up its set weight point so you are better prepared if things go wrong again in the future. If restricting calories does not work, what does?
Insight #2: Insulin plays a crucial role in determining your weight
One new insight is that insulin levels in our blood play a key role in determining our weight. Insulin is a hormone secreted by the pancreas in response to a rise of glucose in the blood. Insulin delivers the message to our cells to take glucose out of the blood and into the cells – either to use as energy or to store as fat. Sustained levels of excessive insulin will tend to increase fat storage. Certain foods, particularly sugar and refined carbohydrates, raise blood sugar – and thereby insulin – more than other foods. Dietary fats do not raise blood sugar and insulin levels by much. So, fat may not be as bad for you as you thought – provided you choose healthy fats. In other words, what you eat may matter more than the number of calories it contains.
Insight #3: Cortisol raises insulin – which is why stress makes you gain weight
Cortisol is the so-called stress hormone, which mediates the flight-or-fight response, a set of physiological responses to perceived threats. In our hunter-gatherer days, the stress that led to a release of cortisol was often physical: for instance, being chased by a predator. To prepare us to fight or flee, cortisol enhances glucose availability which provides energy for our muscles. Vigorous physical exertion (fight or flight) would burn up the newly available stores of glucose. But in our modern-day lives, we have many chronic, nonphysical stressors that increase our cortisol levels. That means glucose levels remain high, triggering the release of insulin. And an increase in insulin will make you gain weight.
Insight #4: Exercise works – but not in the way we expected
Our assumption was that by increasing exercise, we are able to burn off the excess calories that we eat. In practice, exercise does not burn that many calories – running for one kilometre burns about 70 calories which is roughly equivalent to eating one egg. On top of that, exercise makes us hungry and we feel we deserve something to eat. And we compensate for all that exercise by moving less the rest of the day. So, based on the calories in, calories out theory, exercise doesn’t really work to make us lose weight. However, exercise does have a positive impact on weight loss by burning glucose before it has a chance to be stored as fat just after a meal. Recent research suggests a simple walk after a meal can help blunt the immediate glucose spike after that meal and significantly lower overall levels of insulin. Exercise also has been proven to reduce stress, thereby lowering levels of cortisol and insulin. Over and above any positive impact on weight loss, exercise is extremely good for your health.
Insight #5: Our microbiome can influence our ability to lose weight
The trillions of microbes inside of our gut play many very important roles in our body. Not only does our microbiome regulate our metabolism and help us absorb nutrients from food into the body, it can also influence whether we are lean or obese. Though researchers have shown there is a link between the gut microbiome and weight loss, there is still much we don’t know. One question, for example, is whether our microbes are able to manipulate our eating behaviour. Our sugar cravings may come from the signals send to our brain by microbes that need sugar for their survival. That puts a different spin on our addiction to sugar! Even though much is still unknown, improving our gut health and the diversity of our microbiome may be a new avenue to change our tastes and eating behaviour for the better.
Conclusion
Based on these insights, we now have access to more effective approaches for sustainable weight loss. In my upcoming blogs, I will delve deeper into what those approaches look like in practice. Personally, I’m very happy I now have a good scientific reason not to go on a starvation diet in order to lose weight!
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