"Fat people just need more self-control."
"It's a matter of personal responsibility."
"It's simple, eat less."
These are just some of the 1.946 reader comments on the article about weight loss injections which I wrote last year.
Many people, including some medical experts, believe that obesity is solely a matter of willpower.
Eight out of ten respondents believe that obesity can be completely prevented by lifestyle changes alone, according to research conducted in the United Kingdom (UK), Australia, the United States (US), and New Zealand, published in the medical journal The Lancet (The Lancet).
This kind of thinking is disturbing to Bini Suresh, a dietitian who has worked with obese and overweight patients for 20 years.
Suresh believes that willpower is only a small part of a much more complex picture.
"I often see patients who are extremely motivated, well-informed, and working hard, yet still struggle with excess weight," she says.
"Terms like 'willpower' and 'self-control' are misleading," agrees Kim Boyd, director of the international organization's medical department. Weight Watchers which deals with obesity issues.
"For decades, people have been told that they should eat less and move more and that they will lose weight, but obesity is much more complex," the doctor points out.
She and other experts I spoke with point out that there are a whole range of reasons why someone is obese, many of which are not yet fully understood.
However, what is certain is that living conditions and predispositions are different.
The British government is trying to solve the problem through legal measures.
The latest measure, a ban on advertising junk food on television before nine o'clock in the evening, as well as a complete ban on promotions on the internet, came into effect on January 5 in the UK.
However, many believe that even these measures will not be enough to tackle the already huge obesity problem in the UK, where more than a quarter of adults are obese.
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Battle with biology
"The number of pounds people gain depends largely on genes, and they are relevant to each of us," explains Sadaf Farooqui, an endocrinologist.
She treats patients who are severely obese and have associated endocrine disorders, and also leads the Genetic Obesity Study at the University of Cambridge.
Certain genes influence brain pathways that regulate feelings of hunger and satiety, in response to signals sent to the brain by the stomach, the professor explains.
"Variants, or changes, in these genes are present in obese people, which means they feel hungry more often and have a harder time feeling full after a meal."
Perhaps the most important of these genes, at least among those identified so far, is the MC4R gene.
Approximately one fifth of the world's population has a mutation in this gene, which encourages overeating and reduces the feeling of satiety.
"Other genes affect metabolism, or how quickly we burn energy," adds Professor Faruqi.
"This means that some people gain more weight and store more fat while eating the same amount of food as others, or burn fewer calories through exercise," he explains.
She estimates that there are probably thousands of genes that affect body weight, while science currently knows in detail only 30 to 40 of these genes.
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Scientific evidence of the yo-yo diet effect
However, genetics is only part of the story. about obesity.
Each of us has a body weight that our brain understands or considers appropriate, regardless of whether that weight is healthy or not, explains Andrew Jenkinson, a bariatric surgery expert and author of Why do we eat too much? (Why We Eat Too Much).
This is known as the "set" or predetermined weight range theory.
"That target body weight is determined by genetics, but also by other factors, such as the environment in which we eat, stress levels, and sleep quality," he says.
This is why body weight acts like a thermostat - the body tends to maintain that desired range.
If your weight falls below that "set" value, hunger increases and your metabolism slows down, just like a thermostat turns up the heat when it's too cold.
Once that value is "set," it is extremely difficult to change it solely through willpower, claims Dr. Jenkinson.
This theory can also explain the yo-yo effect of dieting.
"For example, if you weigh 127 pounds and your brain 'wants' you to weigh 127 pounds, and you go on a low-calorie diet and lose 13 pounds, your body's response will be the same as if you were starving," he explains.
"The body then reacts with a strong, almost insatiable appetite, increased food cravings, and a slowed metabolism," he adds.
"Those hunger signals are just as powerful as thirst signals, and they're there to help us survive, and an insatiable appetite is something that's really, really hard to ignore."
When it comes to the scientific explanation for this phenomenon, Dr. Jenkinson points to the role of leptin, a hormone produced by fat cells.
"It acts as a signal to the hypothalamus, the part of the brain that basically controls our 'set' body weight, and tells it how much stored energy the body has."
"The hypothalamus then reads leptin levels and, if it determines that we are storing too much energy or too much fat, it automatically changes our behavior by reducing appetite and speeding up metabolism."
That's how leptin is supposed to work.
However, in practice this often fails, especially in Western countries where food is available at every turn, he explains.
The reason is that the signal sent by leptin goes along the same path as the insulin signal.
"If insulin levels are too high, it actually 'dilutes' the leptin signal and suddenly the brain can no longer recognize how much fat is stored in the body."
The good news is that this body weight target is not fixed and can be gradually changed through ongoing lifestyle changes, better sleep quality, stress reduction, and long-term healthy habits.
Much like turning the thermostat to a different temperature, over time, slow and consistent changes can help the body accept a new, healthier weight range.
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The rise of obesity in the UK
However, none of the above alone explains the sudden increase in the number of obese people, because ultimately, our genes and biological makeup have not changed.
Over the last decade, there has been a steady increase in the number of adults classified as overweight or obese.
Analysis by the Health Foundation in 2025 shows that more than 60 percent of adults in the UK now fall into this category (including around 28 percent who are obese).
This trend can be partly attributed to the sheer quantity and accessibility of poor-quality, high-calorie food, especially ultra-processed foods.
When you add to this the aggressive marketing and advertising of fast food and sugary drinks, increasingly large portions, and limited opportunities for physical activity (often due to urban conditions and lack of time), you get this combination of extremely bad circumstances.
"We have become more obese as a population and, of course, those who have a greater genetic predisposition have gained weight," says Professor Farooqui.
Public health experts call this set of circumstances the obesity environment, a term first used in the 1990s, when researchers began linking rising obesity rates to external factors such as food availability, marketing, and urban environments.
Many experts argue that the combination of these factors creates constant incentives for overeating and physical inactivity, making it extremely difficult for even highly motivated people to maintain a healthy body weight.
All of this also explains why willpower has become such a problematic concept.
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Discussion of personal responsibility
Sitting in her office at Newcastle City Council in England, Public Health Director Alice Wiseman sees food all around her.
"There are cafes, bakeries, fast food restaurants."
"You can't go to school or work without passing by a place that sells food."
"Visibility is important, because if you pass a lot of fast food places on your way to work, you're more likely to buy something."
"The body reacts almost automatically to the food in the environment."
In the town of Gateshead in England, where Wiseman is also in charge of public health, no new takeaway permits have been issued since 2015.
However, nationwide, the fast food and delivery industry has continued to grow and is now worth around €26,5 billion annually.
The majority of food advertising spending in the UK is on products high in fat, salt and sugar, such as sweets, sugary drinks, fast food and snacks, according to the latest annual communications market report from the UK Communications Regulatory Authority (Ofcom).
However, Wiseman believes that new measures restricting the advertising of fast, or officially "less healthy" foods on television and the internet may only yield limited results.
Last year's report by the Food Foundation also showed that, on a per calorie basis, healthier foods are more than twice as expensive as less healthy foods.
"In families on a tight budget, it's very difficult to afford a healthy diet," Wiseman says.
"I'm not saying that personal responsibility has no role, but when you think about it, we have to ask ourselves what has actually changed."
"It's not like we've all suddenly lost our willpower," he points out.
Suresh agrees with that.
"We live in an environment that is designed for overconsumption."
"Obesity is not a character flaw, but a complex, chronic condition shaped by biology and the environment that encourages obesity."
"Willpower alone is not enough, and reducing weight loss solely to a matter of discipline is harmful."
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However, others have a different understanding of the term "willpower".
Many people who are overweight today probably wouldn't have had that problem 40 years ago, says Professor Keith Frayne, author of the book A calorie is a calorie (A Calorie is a Calorie).
"It's the environment that has changed, not their willpower or anything else," he says.
"But I worry that if 'willpower' is completely dismissed as a factor, it may make it too easy for people to settle for a body weight that may not be desirable or healthy," he adds.
It calls on large databases of people who have successfully lost weight and maintained that weight long-term.
He cites the National Weight Control Registry in the US as an example, which contains data on more than 10.000 participants.
"These people say it's hard to lose weight, and even harder to maintain the weight you've achieved."
"I imagine many of them would be quite offended if someone told them that willpower had nothing to do with what they achieved."
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'You can't force people to be fit with laws'
A broader question also arises - how much responsibility the state should have.
Wiseman believes that laws are an important tool in the fight against obesity, noting that promotions like "buy one, get one free" encourage impulse buying.
Introducing new laws is not the right way to go, argues Gareth Lyon, director of the health and social care sector at the right-wing think tank. Policy Exchange.
"You can't force people to be fit through laws," he says.
"Banning and taxes on the food people enjoy only makes life harder, less enjoyable and more expensive at a time when the UK is already facing a cost of living crisis," he added.
Christopher Snowden, director of lifestyle economics at the right-wing Institute for Economic Affairs, also believes that obesity is an "individual problem" and not a public health issue.
"(Obesity) is a consequence of the choices an individual makes," he claims.
"So, ultimately, you can't go much further than the individual."
"I think the idea that the state is responsible for making people slimmer is quite bizarre and I would like to see a serious, independent assessment of these policies, and if they are shown not to be working, they should be abolished," he says.
As for willpower, it will always play a role, and the only difference is the importance that experts attach to it.
Bini Suresh believes that willpower is only a piece of a much broader mosaic, and that the first step is educating people about all the other factors.
"This view shifts the focus from a moral judgment about willpower to compassion, a scientifically based support system, which provides a better chance for long-term success."
There are also ways to strengthen willpower, says Eleanor Bryant, a psychologist at the University of Bradford in England.
"It's not constant, willpower is affected by mood, fatigue, and, when it comes to nutrition, how hungry you are..."
How you think about it is also important.
There are two types of willpower - flexible and rigid.
Someone who is rigid sees it in black and white.
"If you succumb to temptation, you have practically given in."
"You eat that cookie and then keep eating."
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In psychological terminology, this is called disinhibited eating, or eating without internal mental or emotional inhibitions.
"Whereas a flexible person says, 'Okay, I ate one cookie, but I'll stop there,'" Bryant explains.
"It goes without saying that a flexible approach is much more successful."
"Exercising willpower around food is probably more difficult than in other areas of life," he adds.
Bini Suresh believes the same, but points out that when people understand the limits of willpower, their ability to use it actually becomes stronger.
"When patients understand that their struggle is rooted in biology, not a lack of discipline, and when they receive support through a balanced diet, meal patterns, psychological strategy, and realistic goals, their relationship with food improves significantly," he concludes.
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