What’s the ‘weight set point’, and why does it make it so hard to keep weight off?
If you've ever tried to lose weight, only to find that the pounds come back almost as quickly as they left off, you're not alone.
In fact, research confirms the challenge of maintaining weight loss, including an analysis of 29 long-term weight loss studies that found that more than half of the weight lost by participants regained it within two years, and more than 80% of the weight lost was regained within five years up.
When we gain weight back, we tend to blame it on a lack of willpower.
But there is a scientific basis for many people regaining their previous weight after dieting, and understanding the science — known as the weight set point theory — is key to achieving long-term weight loss.
What is a weight set point?
We each have a predetermined weight—a set point—and our bodies protect it. This is the weight you'll remember for a long time as an adult (over 20), and it's the weight you'll remember bouncing back from any diet.
It is programmed very early in life – specifically in the first 2,000 days of life – from conception to the age of five. Our genes play a role in programming our weight set point. Just as our DNA determines whether we are shorter or taller than other people, we are born with a tendency to be thin or overweight. But our genetic makeup is a predisposition, not an inevitable destiny.
The weight set point is also influenced by environmental factors to which genes may be exposed during pregnancy and the first few years of life. It explains why some children who eat a poor diet are more prone to unhealthy weight gain (due to their genetic makeup), while others are not. Research shows that unhealthy weight gain early in life may continue throughout adolescence and adulthood.
Finally, our weight is influenced by the environment itself. For example, an unhealthy diet, a sedentary lifestyle and insufficient sleep can cause your weight setpoint to increase by 0.5 kg per year over time.
Our bodies work hard to keep our weight near our set point by tuning our biological systems, regulating how much we eat, how we store fat and expend energy. It stems from our hunter-gatherer ancestors, whose bodies developed this survival response to adapt to periods of deprivation when food was scarce to prevent starvation. Unfortunately, this means that our bodies are very good at preventing weight loss rather than weight gain.
How Our Bodies Protect Our Set Points When We Diet
When we change our diet to lose weight, we take the body out of its comfort zone and trigger its survival response. It then counteracts the weight loss, triggering multiple physiological responses to preserve our weight and “survive” hunger.
Our body's survival mechanisms want us to regain lost weight to ensure we survive the next famine (diet), which is why many people who regain weight after dieting end up weighing more than they started.
Our bodies achieve this result in a number of ways.
1. Our Metabolism Slows, Our Thyroid Misfires
Our metabolic rate—how much energy we burn at rest—depends on how much muscle and fat we have. Muscle is more metabolically active than fat, which means it burns more calories. Usually, when we diet to lose weight, we lose both fat and muscle, and the loss of calorie-burning muscle mass slows down our metabolism, which slows down the rate at which we lose weight.
Research also shows that with every dieting attempt, the rate at which we burn food slows down by 15%, and our metabolism does not recover even after we regain the weight. But exercise can help restore and rev up our metabolism because it improves our muscle-to-fat ratio.
Dieting also affects our thyroid — the gatekeeper of our metabolism. When our thyroid is functioning normally, it produces important hormones that control our energy levels and metabolism, but when we restrict food intake, fewer hormones are produced, reducing the amount of energy we burn at rest.
2. We use energy differently
Our bodies primarily burn fat stores at rest, but when we diet and start losing weight, our bodies adapt for protection. It switches from using fat as its energy source to using carbohydrates and retaining its fat, reducing the amount of energy burned at rest.
3. Our appetite hormone adjustment
Orexin plays an important role in weight management. When we're hungry, the stomach releases a hormone called ghrelin to let our brain know it's time to eat. Our gut and fat tissue also release hormones that signal satiety and tell us it's time to stop eating.
However, when we diet and deprive our bodies of food, these hormones work differently to protect our set weight, suppress satiety and tell us to eat more. Like our metabolism, appetite hormones don't return to the same levels they were before the diet, meaning hunger can take over, even after the weight is regained.
4. Our adrenal glands work differently
Our adrenal glands manage the hormone cortisol, which it releases when a stressor such as dieting is applied. Excess cortisol production and its presence in our blood can lead to weight gain as it plays a vital role in how our body processes, stores and burns fat.
5. Our brains work differently
Typically, diets tell us to limit certain foods or food groups in order to reduce our calorie intake. However, this heightens the activity of our mesolimbic circuits (the reward system in our brains), causing us to overeat the foods we've been told to avoid. This is because foods that give us pleasure release feel-good chemicals called endorphins, as well as a learning chemical called dopamine, that when we see them, they Makes us remember — and succumb to — that feel-good response.
When we diet, activity in our hypothalamus — the clever part of the brain that regulates mood and food intake — also decreases, reducing our control and judgment. It often triggers a psychological response known as the “what the hell effect” – when we obsess over something we don't think we should be doing, we enter this vicious cycle, feel guilty about it, and then Want to do more.
take home message
We are wired to protect our weight set point. Traditional diets, including the latest hype around “intermittent fasting” and “keto,” do not promote healthy eating or address weight set points. You will eventually regain the weight you lost.
Just as problems evolve, so do solutions.
Long-term successful weight loss comes down to:
Follow evidence-based care from healthcare professionals who have studied the science of obesity, not celebrities
Lose weight in small, manageable chunks that you can maintain, specifically a weight loss period, followed by a weight maintenance period, and so on until you reach your goal weight
Make gradual changes to your lifestyle to ensure you develop habits that will last a lifetime.
Nick Fuller is Director of Research Programs at the Charles Perkins Center at the University of Sydney. He has received external funding for projects related to the treatment of overweight and obesity and is the author and founder of the Interval Weight Loss Program. This article first appeared on The Conversation.