In this week’s Ask an Expert, Clinical Director of Streamline and Bariatric Surgeon Mr Guy Slater delves into the topic of dieting; looking at genetic predispositions to weight gain, the myth surrounding calorie counting and the links between exercise and weight loss.
Why doesn’t dieting work?
The simple answer is Evolution.
Quite simply, we have evolved over millennia to survive famine. This evolutionary background is key to understanding why dieting doesn’t work.
Common questions about dieting
When dieting, you may ask yourself:
- If dieting is such a good thing for my health, why is it so terribly difficult?
- Why do I see all the same faces at Slimming World?
- Why do I feel like I’m in a never-ending fight with my appetite?
- Why am I always thinking about food?
The evolutionary survival mechanism
Evolution and survival are central to why dieting doesn’t work. Always thinking about food when dieting is normal, without it we would be dead. These thoughts are triggered by the complex relationship between your brain and body, mediated by nerves and gut hormones including ghrelin, leptin, GLP-1 and insulin. 24/7 your body, monitors your energy intake and expenditure very closely, just as it does for other vital functions such as temperature, aiming to maintain your weight at a set point, not losing, not gaining.
Understanding the difficulty of weight loss
Any diet of more than a day or two, sets alarm bells ringing, making your body think it’s facing a life ending famine. To survive the famine, via these thoughts, your body makes you look for calories; that’s how your ancestors over many generations survived war, pestilence, crop failure and so on. This survival mechanism is a key reason why dieting doesn’t work.
The good news, despite for years and years saying otherwise, is that we are beginning to understand that losing weight is much more difficult than eat less, exercise more. We now know that does not work and neither does calorie counting.
It must be a relief to anyone who has had a life-long struggle with their weight facing prejudice and stigmatisation, that we no longer think; with just a little more will power, strength and determination you could lose weight and maintain that weight loss long-term.
To understand why dieting doesn’t work, we need to consider genes, metabolism, the role of exercise and western diets. Understanding how each of these contributes explains not only why dieting is so rarely successful, but also why some people gain weight in the first place.
Some miserable supposed health experts don’t buy the genetic argument that some people are genetically predisposed to weight gain. If that’s the case why do Labradors struggle with their weight so much, always hungry, while other breeds don’t? Selective breeding in Labradors has created not only very loveable features but also a voracious appetite that owners can find difficult to manage.
Genetic predisposition to weight gain
To understand why dieting doesn’t work, we need to consider genes, metabolism, the role of exercise, and western diets. Understanding how each of these contributes explains not only why dieting fails but also why some people gain weight in the first place. We don’t yet fully understand all the specific genes or combinations of genes that make individuals prone to weight gain, but we do know that there are some specific individual gene mutations, such as the MCR4 gene that can make people prone to obesity.
As before it’s a survival of the fittest evolutionary argument that can help explain why some groups of people are especially susceptible to a western diet. South Sea Islanders in the Pacific Ocean region have obesity rates that are much higher than the global average. It is thought that this reflects their journey thousands of years ago, across thousands of miles of open sea to the islands. Many of the migrants, would have died on the journey from starvation, with only the most genetically pre-disposed to survival from famine making it to land to populate the islands. For thousands of years, they remained well on a simple agrarian diet until hit by a tsunami of ultra-processed, high-sugar, high fat processed foods from the West’s food industry, which took full advantage of their genetic propensity to gain weight.
Why has obesity skyrocketed in recent decades?
I can hear the sceptics asking “but, if it’s all about genes and genetic inheritance, why is it only recently that obesity has become so widespread?” There is a very clear answer, it dates back about 30 years to the eighties, when our healthy diets were hijacked with ultra-processed, high fat, high sugar, chemically laden foods pimped to us by the all-powerful food industry, using glamorous advertising and marketing. This contributes to why dieting doesn’t work for many people.
Before then, approximately 1 in 10 people struggled with their weight, now it’s 3 in 10. Those 3 in 10 who are genetically pre-disposed to obesity have bodies which are particularly susceptible to the chemicals in ultra-processed foods. Like a Trojan horse, the chemicals in UPF have infected their bodies, like a computer virus hacking the body’s normal appetite and satiety mechanisms. No longer satiated by these alien foods and driven to eat more, genetically susceptible individuals, gain large amounts of weight. Not only do these foods cause weight gain, they also predispose them to serious metabolic illnesses including diabetes.
If that’s not bad enough, the evidence shows that even if you don’t gain weight with a diet rich in ultra processed foods (UPF), you are still at a much greater risk of metabolic illness than people who eat well, avoiding UPF. For a much more complete understanding I would recommend Chris Van Tulleken’s book Ultra-processed People.
The myth of calorie counting
Calorie counting seems logical but fails to address why dieting doesn’t work. Again, I can hear the sceptics “What about Calorie counting, surely, it’s common sense”. Reduce calories with a diet, increase energy through exercise create a calorie deficit and lose weight. And it would be that easy if we were simple machines, energy in, energy out, but we’re not.
We are all born with different metabolic rates or using the machine analogy fuel efficiencies, probably determined by our genes. Some people have gas-guzzling Ferrari like metabolisms, able to eat whatever they like and gain no weight, others have the metabolism of a hyper-efficient supermini barely able to avoid weight gain. Unlike cars which have fixed fuel efficiencies, our metabolism can adapt and change in response to diets and famines.
The role of metabolic adaptation
We might start adult life with a Volvo-like robust metabolism, progressing through multiple diets to the hyper-efficient, miserly fuel consumption of a mini. This should not surprise us, it’s the body’s normal response to famine, decrease metabolic rate during the famine to offset the lower calorie intake and maintain a lower metabolic rate than pre-famine just in case there’s another famine soon. In the next famine decrease metabolic rate again. This is the very mechanism that underpins yo-yo dieting with patients gaining weight after each and every diet they complete, until they have to be on ultra low-calorie diets such as the Cambridge diet or lighter diets. Even on these very low calorie diets their weight loss will be very slow because their metabolic rate is so low. This process has a name metabolic adaption.
But it’s not just metabolic adaption that makes calorie counting fail. Scientifically, the data we use to measure calories in food is hopelessly inaccurate. Not only is there a significant difference between the number of calories that enters your mouth and the number you absorb, there is a wide difference from person to person. It is especially difficult to estimate the number of calories in whole foods, the ones we should be eating, like fruit, vegetables and nuts while paradoxically it’s much easier to estimate the number of calories in the ultra-processed foods, that we really shouldn’t be eating. Lastly calorie counts don’t take into account food quality with for example a hamburger and an avocado having similar calorie scores. An avocado with all it’s good vegetable fats is good for us, while we really shouldn’t be eating ultra-processed hamburgers very often at all.
Exercise and weight loss
I can hear you asking, but surely if nothing else works I can still lose weight burning calories with exercise. I hesitate to disappoint. Exercise is the most beneficial intervention we can make to protect our health and live well for longer. All of us should be taking regular aerobic exercise and strength training every week, but aerobic exercise seems to contribute very little to weight loss. Just like repeated dieting reduces metabolic rate, ultimately causing weight gain, our bodies are just too smart and through metabolic adaption will decrease our daily metabolic rate to account for the calories spent exercising. Despite this, many find that exercise alone doesn’t resolve why dieting fails.
But all is not lost, there is good evidence that individuals can increase their metabolic rates by building muscle with strength training. Muscle is much more metabolically active than fat and other tissues. If there is only one message that you take from this blog, I hope it is “get to the gym, pump iron and build muscle”. It will be time and energy well invested.
I’m sorry if you have found this explanation to the question “why doesn’t dieting work?” depressing, but maybe, just maybe with great patience, by avoiding UPF completely and sugar as much as possible combining a good diet, cooking from scratch with whole ingredients and regular exercise, especially strength training, you may slowly lose weight.
The role of GLP-1 drugs and surgery
Until recently, there were no drugs that helped at all, but now we have the GLP-1 type drugs, Wegovy, Saxenda and Mounjaro that can be very effective, but like dieting they aren’t a short-term fix. In my opinion they will need to be taken intermittently, indefinitely a bit like a statin or blood pressure medication. If you want to use them, all the evidence shows that they are much more effective if used as part of a program with lifestyle and dietary change.
Lastly, we know surgery is effective. The evidence for it is overwhelming. It can give long-lasting weight loss, without medication, but just like medication the most powerful benefit of surgery comes from combining it with complete dietary and lifestyle change, exercising, eating whole foods avoiding sugar and UPF.
If you’re ready to take the next steps to achieving significant weight loss, call us on 03330163030 or fill out the form below.
Guy Slater
Guy Slater is one of the founders of Streamline and has been a bariatric surgeon for 20 years. Guy has served as a consultant surgeon since 2004 and has performed more than 2500 bariatric procedures resulting in over 1000 laparoscopic Roux en-Y bypasses, over 250 laparoscopic sleeve gastrectomy’s and 500 laparoscopic adjustable gastric bands including the more difficult high BMI patients. Much of his time is now spent concentrating on revision bariatric surgery, including the gastric band to bypass and sleeve to bypass.