Weight loss: The real reasons the kilos creep back on

Yo-yo dieting might not be your fault – new research shows fat cells remain primed to regain weight.

'When people lose weight, their fat cells shrink but don’t disappear,' says Dr Linia Patel. Picture: Getty Images

Are you someone who manages to lose weight on a diet, only to find it creeps back on almost as quickly as it disappeared? It’s a frustrating cycle familiar to many of us who discover that the real challenge isn’t losing weight, but avoiding piling the kilos on again.

A review of 29 weight-loss studies in the journal Medical Clinics of North America found that more than half the weight lost by overweight people on any diet was typically regained within two years.

While a lack of willpower tends to be blamed for these setbacks, emerging evidence suggests other factors are at play and that our propensity for putting weight back on might actually be driven by lasting changes to the DNA of our fat cells.

“When people lose weight, their fat cells shrink but don’t disappear,” says Dr Linia Patel, a researcher in the department of clinical sciences and community health at the Universita degli Studi di Milano in Italy, and a spokesperson for the British Dietetic Association.

“These cells remain primed to store fat again, which can make regaining lost weight easier – it’s referred to as fat cell dynamics.”

In a recent study published in the journal Nature, scientists at the Federal Institute of Technology Zurich in Switzerland, along with other institutions, delved deeper into why this might happen. They analysed fat tissue obtained from 20 people with obesity just before they underwent bariatric surgery – a procedure to make the stomach smaller so that less food is needed to feel full.

They also analysed fat tissue from 18 people of a healthy weight. Two years later, when the obese participants had lost almost 25 per cent of their initial body weight, the researchers collected additional fat tissue samples from all participants.

Analysis revealed differences in the activity of RNA molecules – genetic regulators that influence how fat cells use or store fat – between people with obesity and those of a healthy weight. They found that differences within the fat cells persisted even after two years of significant weight loss.

Researchers’ findings suggest obesity-linked genetic changes may predispose individuals to future weight gain.

Dr Laura Catherina Hinte, a researcher in nutrition and metabolic epigenetics and lead author on the paper, explained that obesity appeared to cause RNA changes “within fat cells themselves, which may be linked to future weight regain”.

Hinte and her colleagues also looked at RNA activity in obese mice that had initially been fed a reduced calorie diet to lose weight. When the newly slimmed-down mice and healthy weight mice were put on a high-fat diet for four weeks, results showed that the previously obese mice regained an average 14g in weight compared with only 5g gained by the healthy mice. Moreover, fat cells from the formerly obese mice absorbed more fat and sugar than those from the healthy mice – changes thought to be influenced by RNA activity within the cells. According to the researchers, these findings suggest that obesity-linked genetic changes may predispose individuals to future weight gain. As Hinte explains, it is “another puzzle piece that could help to explain why maintaining lifestyle changes is challenging”.

Unfortunately, evidence shows that sustaining weight loss is hard regardless of the method you choose to lose weight. Following a very low calorie diet, which usually entails sticking to no more than 800-1200 calories (3344-5016kJ) a day, leads to upwards of 26 per cent weight regain in some people, with others gaining even more than their pre-diet weight, according to a study in Obesity journal.

Similarly, researchers at the University of Pennsylvania’s School of Medicine found that dieters who attended weekly weight management programs typically regained 30-35 per cent of the weight they initially lost within 12 months. Even those who shed several kilos on weight-loss drugs like Ozempic may regain it quickly if they stop taking the drug, according to research published in the Diabetes, Obesity and Metabolism journal.

Not that we can blame our DNA entirely. As Hinte explains, our tendency to yo-yo diet also involves other factors.

“It is very difficult to fight hunger or appetite as it goes against evolution or biology itself,” she says. The reality is that there are no quick fixes.

“Lifestyle changes which include both a healthy diet and exercise, if you can stick to them, are the best way to reduce body weight long term,” Hinte advises.

Here’s why else you might be regaining the weight you have lost:

Your weight-loss diet could be too restrictive

Many traditional diets rely on willpower and a rigid “diet mentality” to stick to a plan for a set period, Patel says. It can mean that by the time you have reached your target weight you are fed up with thinking about food and weight – you experience a “diet burnout”, essentially. “While they may work short term, these approaches rarely teach the sustainable habits needed for long-term success,” she says.

“When life returns to normal, people often lack the mental tools to manage their weight effectively and the all-or-nothing mindset common with strict dieting often leads to reverting to old eating patterns.”

High stress levels cause a higher level of the hormone cortisol to circulate in our bodies, which leads to sugar cravings.

You’re stressed and not getting enough sleep, which makes you hungry

Eli Brecher, a registered nutritionist, says that many yo-yo dieters who seek her advice lead stressful lives.

“Too much stress is likely to lead to emotional eating, particularly of foods high in fat and sugar, which plays havoc with weight loss and regain,” she says.

“When our stress levels are high and there is more of the hormone cortisol circulating in our bodies, it affects our body’s ability to regulate blood sugar and leads to cravings, and in turn more weight is gained.”

Even if you have lost lots of weight, poor sleep patterns make it more likely that the kilos will creep back on.

“A lack of sleep increases levels of the hunger hormone leptin giving rise to cravings for sweet or calorific snacks,” Brecher says. “It is vital that stress and sleep are addressed to keep weight off long-term.”

Your body has reached its unique ‘set point’ weight

One theory put forward by many researchers is that our bodies have a unique, biologically determined weight range, or “set point”, that it naturally strives to protect – it’s the weight you tend to bounce back to after you have been on any diet.

Our set point weight is established in childhood – some researchers have even suggested as early as the womb – but it can be influenced by genetics, hormones, behaviour and lifestyle factors.

“A diet on which you lose a lot of weight quickly won’t actually change your set point as your body is very clever and will eventually adjust to require fewer calories to function efficiently,” Brecher says.

“In order for weight loss to continue or for weight regain to be avoided, you would have to slash your calorie intake even further, which sends you spiralling down a vicious cycle of deprivation.”

However, emerging research suggests it may be possible to shift your set point over time, and an animal study in Obesity is among those showing that weight loss after bariatric surgery can reset your set point.

“Maintaining weight loss over a long period will help the body to adjust to a new, lower set point,” Patel says. “Exercise and a nutrient-dense diet can influence hunger and appetite hormones, potentially helping to reset the set point weight.”

You aren’t active enough

While diet is the key factor for weight loss, exercise is essential for weight maintenance. A study from the University of Colorado revealed that 300 minutes a week (about 40 minutes daily) of physical activity did more to maintain substantial weight loss in participants compared with those who only dieted.

Exercise was also shown to prevent an increase in the number of fat cells in dieters, whereas sedentary lifestyles led to more new fat cells forming – a process that, according to researchers writing in the American Journal of Physiology, could accelerate weight gain.

“When you lose weight, your body burns fewer calories due to a reduction in body size and metabolic rate, a process known as adaptive thermogenesis,” Patel says.

“This can make sustaining weight loss more difficult, especially if you don’t have enough muscle mass to support your metabolism. But evidence shows that regular physical activity helps to prevent weight regain.”

Levels of leptin, an appetite-suppressing hormone, were also found to increase in a group of overweight men and women who worked out for 300 minutes a week, while those who worked out less or not at all experienced no such change.

Authors of this study from the University of Kentucky reported that exercise helped the dieters to regulate their desire to eat, preventing kilos from reappearing.

A position statement in the Medicine and Science in Sports and Exercise journal suggests a minimum of 250 weekly minutes of exercise to maintain weight loss.

Resistance training will help prevent weight gain. Picture: Getty Images

Lifting weights is particularly helpful for maintaining weight loss

If there’s one activity that will help with preventing weight regain, it’s resistance training. One of the main reasons people who lose lots of weight eventually regain it is because they lose muscle mass along with body fat through dieting. Since your muscles help to burn calories, it’s important to keep them strong.

“Muscle tissue is more metabolically active than fat tissue, so building and maintaining muscle tissue through resistance exercise is a key strategy for keeping weight off,” Patel says. “If you don’t, once you start to eat normally again, you won’t have the metabolic tissue to burn up fuel and weight will creep on.”

Researchers who analysed data on 12,000 midlifers for a study in PLOS Medicine showed that those who did regular muscle-strengthening exercises of any kind for a weekly total of 1-2 hours were better able to control their body weight and were up to 30 per cent less likely to become obese over time than people who did no resistance training.

High-quality, nutrient-dense foods can have a powerful effect on weight maintenance.

You’re not eating enough wholegrains, protein and fibre

It’s not just the amount of food consumed, but the quality of it that can affect your ability to keep weight off. “It’s a really common error to focus on calorie reduction and not on diet quality when trying to lose weight,” Patel says.

“This can help with initial weight loss but can backfire later on when you try to maintain a new weight.”

A diet with plenty of fibre-rich wholegrains, seeds, nuts, fruit and vegetables as well as lean and plant-based protein such as pulses, tofu and yoghurt can have a powerful effect on weight maintenance.

“High-quality, nutrient-dense foods such as these play a crucial role in regulating our hunger hormones,” she says. “A healthy balanced diet will manage appetite and make long-term weight loss more achievable.”

It is recommended that we consume 30g of fibre daily, although most UK adults get only 18g in their diet.

Aim for your five-a-day of fruit and vegetables and you should hit that target. In Obesity Reviews journal, nutritionists found that eating plenty of fibre-rich foods such as oats, wholemeal bread, beans, peas and lentils meant dieters were less likely to experience weight regain.

“High-fibre foods take a lot of chewing which stimulates satiety signals and tells us we are fuller sooner,” Patel says. “They also take longer than processed and refined foods to pass through our digestive system so that we stay full for longer and that is a big boost for weight maintenance.”

Women may struggle more with weight maintenance than men

Patel says that women may struggle more than men to keep weight off. “When the brain perceives inadequate nutrition, especially a lack of energy-providing, high-quality carbs, there is a significant drop in the production of kisspeptin, a neuropeptide crucial for regulating sex hormones, and women are more susceptible to the effects of this than men,” she says. “Kisspeptin also plays a key role in maintaining healthy blood sugar levels, in appetite regulation and body fat levels.”

It’s a physiological sensitivity that explains why some women struggle to keep weight off with crash diets or intermittent fasting regimens.

“In women, energy deficits from strict fasting-style diets can raise levels of the stress hormone, cortisol, which signals the body to hold onto fat,” Patel says.

“A more balanced and long-term approach to dieting is usually more effective for women looking to make sustainable changes to their body weight and composition.”

The Times