Why is it so hard to lose weight and keep it off?
the good news is that it’s not because you lack willpower
Everyone I know has, at some point or other in their life, looked in a mirror and decided that they need to shape up and lose a few pounds. I suspect that it was not one-off experience. We are all pretty hopeless at attaining and then maintaining a healthy body weight over the course of our adult lives. It always seems to be creeping up.
Yet most off us know what we need to do — eat more healthily and exercise a little more — so why is it so hard?
The good news is that it is not simply a lack of willpower or that we have a deficiency in the self-motivation department of our personality. The bad news is that our bodies, brains and the whole of the modern world is out to sabotage our good intentions, and without a huge dose of insight, we are never going to triumph.
“Calories are the currency of life,” says Herman Pontzer, a renowned evolutionary biologist, and the calories that we consume are converted into energy by the trillions of cells in our bodies. The amount of calories we each need simply to keep us alive is known as our resting metabolic rate. Our brain, liver, kidneys and heart actually use 60–80% of our daily calories, the remainder being used by our digestive system and our muscles.
This resting metabolic rate varies widely between people and we don’t really know why. It depends to some degree on our sex, age, genes and the ratio of lean muscle to fat tissue in our bodies, and generally people with a higher BMI have a higher metabolism since it takes more calories to run a bigger body than a smaller one.
It seems that it is almost impossible to exert any sort of control over our resting metabolic rate — boosting the metabolism through exercise or food supplements in any meaningful way is a myth. If we build more lean muscle, the increased energy demands of our new body is matched by an increase in appetite.
Unfortunately though we can lower our resting metabolic rate and slow down our metabolism. How do we manage this? Dieting.
The primary job of our brain is to balance our body budget through making predictions about our day to day energy needs. These predictions are based on past experience as well as sensory information from our organs and tissues, nutrient levels, hormone messengers circulating in our bloodstream and neurotransmitters sending messages via our nervous system.
The result is that our brain works flat-out to keep our bodies at a set point weight (± 10lbs). However, our brain has also evolved a very strong defence of the lower limits of what is considers to be a healthy body weight, particularly in terms of fat storage, and so it seems (more bad news) that our set point is ‘floating upwards’ in response to being continually surrounded by great tasting energy dense foods, aggressive food advertising, increasing portion sizes and a sedentary lifestyle.
Weight-loss, regardless of how it is achieved, triggers a multitude of metabolic and behavioural responses that are exceptionally effective at restoring the energy balance and hence returning us to our set point. In reality, after 5 years over 40% of dieters end up heavier than when they started and almost all put most of the weight they lost back on.
Research shows that when we lose weight, our resting metabolic rate slows considerably more than would be expected for a body of the new, lower weight, and this effect lasts for years. Once we have attained our healthy body weight we may always need to eat 200–400 fewer calories per day to maintain our new weight.
On the one hand, our bodies become more efficient. Muscle fibres burn 20–25% fewer calories at rest and during moderate aerobic exercise, for example. On the other, our appetite hormones are disrupted with higher levels of the hunger hormone ghrelin and significantly lower levels of hormones such as leptin and peptide YY which are responsible for suppressing hunger, reducing food intake and increasing our metabolism to burn excess calories.
Our brain also develops a greater emotional response to food. The reward and motivation areas of the brain are more active and the areas involved control are depressed. We genuinely experience more food cravings and the smell, taste, sight and past social experiences we have had with food trigger us to eat more than we need metabolically speaking.
The upshot is that attaining and maintaining a healthy body weight is really, really hard!
So what does success look like? Lifelong changes to our habits and understanding all the powerful ways our brain, body, supermarkets, food advertisers, restaurants and take-away outlets are out to sabotage our best laid plans.
We need to move more, count calories (we are notoriously poor at tracking how much we eat!), eat smaller portions and drink more water. We need to ditch all the ultra-processed foods that have crept into our weekly shopping basket. We should fill up on low energy density foods that nourish our gut microbes such as whole grains (oatmeal scores very highly on the satiety index), fresh vegetables, fruit, beans and pulses, eggs, fish, poultry, raw nuts. Soups and high quality meal replacement shakes are also very effective for keeping us feeling fed and providing lots of nutrition.
In the long-term, the best diet out there is the one you can stick to, whether that be low fat or low carb. There are no magic pills for hacking our metabolism, however sparkly the advert or the influencer!
