The incredible new obesity pills that can help you lose weight WITHOUT dieting revealed by scientists – and they mean you can also avoid worst effects of weight-loss jabs

Plagued by shortages, and with unpleasant potential side effects including nausea and loss of muscle mass, the ‘miracle’ weight-loss jabs – such as Wegovy and Ozempic – may not be quite the panacea many had hoped for.

Indeed, studies suggest these symptoms have caused large numbers of people to stop taking the drugs.

Wegovy, Ozempic and other new weight-loss jabs contain medications such as semaglutide and liraglutide. These mimic glucagon-like peptide-1 (GLP-1), a hormone made naturally in the body that helps slow the passage of food through the stomach – which makes people feel less hungry – and alters the brain’s appetite regulation, so that people feel satiated despite eating less.

But could instead the real answer to easy weight loss be a pill that speeds up our metabolism, so that we simply burn excess fat without the need to exercise or diet?

That is the hope offered by researchers in Denmark who say they have discovered a natural ‘switch’ in our bodies which they can alter to accelerate the speed at which we burn energy (i.e. our metabolic rate) and also to shrink our appetite. Without, it’s claimed, the key side-effects of the weight-loss jabs.

Our weight is largely determined by the balance between the energy we consume, and the amount of energy we expend. When we eat more calories than we burn, we gain weight.

Research shows that in the Western world over the past 40 years, metabolic rates have been steadily slowing – this has been linked to lifestyle factors such as diets of highly processed foods, lack of exercise and sleep and even overheated homes (more on this later).

On the other hand, eating fewer calories and burning more of them by accelerating our metabolic rate should cause weight loss – which is why there is now increasing interest in speeding up our metabolisms medically.

 The newly identified human metabolism switch is called the neurokinin-2 receptor (NK2R). It is found in the central nervous system, particularly the spine.

NK2R’s influence on weight recently emerged after studies found that people with some genetic variants of this switch are unusually prone to becoming obese, the journal Signal Transduction and Targeted Therapy reported in January.

A few weeks earlier scientists at the University of Copenhagen revealed that they had already developed a new drug to block the NK2R receptor. This in turn increases calorie burning in the muscles and body fat.

When the scientists administered the as-yet unnamed drug to animals such as mice and primates, they all lost weight, ate fewer calories and their bodies’ sensitivity to insulin improved (insulin resistance – when cells stop responding properly to insulin – leads to type-2 diabetes) after eight weeks on the drug.

Moreover, as the researchers reported in the journal Nature, their new drug appears to work without causing the two major side-effects seen in GLP-1 ‘skinny jab’ drugs such as Wegovy and Ozempic – debilitating nausea and the loss of muscle mass.

Zach Gerhart-Hines, an associate professor of metabolism at the University of Copenhagen who co-authored the study, said: ‘Doses of Ozempic and Wegovy can cause a significant aversive nauseating response. However, our drug had no such trigger.’

This could be significant, given the findings that many people stop taking the GLP-1 drugs because of their side-effects.

For example data from more than 4,000 patients taking GLP-1 jabs showed that more than two-thirds of them had stopped using them within a year, according to a report from the US pharmacy-business analysts Prime Therapeutics published in 2023.

 The researchers at the University of Copenhagen said they aim to begin clinical trials of the new metabolic-switch drug on humans within two years.

The medication joins two other drugs in development that also aim to accelerate our metabolic rate to boost weight loss.

One of these is a class of drugs called controlled metabolic accelerators (CMAs).

These speed up metabolism by harnessing a natural process in the mitochondria, the ‘batteries’ inside our cells, to boost the way our bodies break down fat and sugar; they also raise the amount of energy that our bodies burn while at rest. Studies are already under way for a daily pill, called HU6, developed by the US firm Rivus Pharmaceuticals.

In September last year, the company revealed that the results of a clinical trial in obese patients who had heart failure suggested that the drug helped them to shed weight. Patients on the highest daily dose of HU6 lost an average of 6.8lb after three months. Crucially, the weight they lost was in the form of fat, rather than healthy muscle tissue.

Sparing muscle is particularly important for heart failure patients, who may already be frail and lack muscle due to the fact that their condition inhibits their ability to exercise.

Previously, in a report in the journal The Lancet: Gastroenterology & Hepatology in 2023, the company reported that side-effects of their HU6 drug include flushing, which a third of participants experienced; diarrhoea, which a quarter reported; and palpitations, which affected around one in ten.

A second approach uses drugs that boost the activity of our metabolism-regulating thyroid hormones. This in turn speeds up our metabolic rates so we shed weight by burning away significantly more calories.

However, both CMAs and this simple-sounding approach have been complicated by the risk of dangerous side-effects.

One early CMA drug, called 2,4-dinitrophenol, while effective, has been linked to the deaths of at least 33 people in the UK – mostly among bodybuilders who use it illegally to strip fat and achieve the ‘ripped effect’ of pure rippling muscle.

In 2024, Jamie George, a gym-owner who had been making the drug in his home and selling it worldwide for four years, was sentenced to 37 months in prison after he pleaded guilty to supplying a dangerous substance to the public. The Stirling court heard expert evidence that the drug carries a high risk of severe toxicity and can cause kidney failure, liver failure, coma and cardiac arrest, even at low doses.

There are also potentially lethal problems involved in using drugs that boost our thyroid hormones to raise our calorie-burning metabolic rates.

As a 2009 research review in the journal Hepatology cautioned, ‘an excess of thyroid hormone is associated with unwanted effects, particularly on the heart (including sudden death) but also on bone thinning and reduced skeletal muscle.’ Scientists have since been trying to create thyroid-hormone boosting drugs (often called thyromimetics) free of such dread problems.

In 2023, researchers at the University of Massachusetts announced they had developed a thyroid-boosting drug that, in lab studies, had dramatically reduced weight in obese mice, without ‘any untoward side-effects’. The developer reported in the journal PNAS Nexus how after five weeks of treatment, the mice’s weight dropped to a healthy normal, even though they were still on the same high-fat diet that had caused them to pile on weight. The rodents’ cholesterol and bodily inflammation also dropped.

A drawback with this drug is that it must be injected directly into the liver on a daily basis, to prevent it poisoning the rest of the body.

Considerable development remains to be done, but the researchers hope to develop their innovation into a practical weight-loss drug.

Dr Adam Collins, an associate professor of nutrition at the University of Surrey, told Good Health that speeding people’s metabolic rates as a weight-loss strategy is an old idea that had become highly discredited.

‘Historically, this has been tried quite widely before – for example, putting overweight people on amphetamine pills – also known as “speed”,’ he points out.

Amphetamine pills were widely prescribed in the 1960s, but proved to be addictive and had dangerous side-effects, such as heart palpitations.

Dr Collins adds: ‘More recently there has been 2,4-Dinitrophenol, which effectively gets people’s bodies to overheat – and equally dangerously, people have tried doing the same by taking excessive doses of the thyroid hormone thyroxine, which regulates the body’s metabolism.

‘With these you are generally cooking yourself.’

He is also sceptical about the newest NK2R drugs: ‘This is currently a hypothetical approach based on animals and I am doubtful as to its rationale and application for humans.’

Yet if there is more work to be done, there is a clear rationale for the growing interest in metabolism-speeding drugs – because our metabolic rates in the Western world have been slowing down over the past few decades This puts us all potentially at increased risk of weight gain regardless of how much we usually eat.

In 2023, a study published in the journal Nature Metabolism, involving more than 1,400 people in Europe and the US, showed that men and women on average now burn 6 per cent less energy while at rest than they did in the past.

Metabolic rate is calculated by measuring how much oxygen you breathe in, and how much carbon dioxide you breathe out while using a calorimeter, which works out how many calories you burn while your body is at rest.

Several modern lifestyle habits are thought to slow metabolic rates – but we can tackle them:

CUT BACK ON SUGARY SOFT DRINKS 

A three-month study of overweight and obese people who were asked to consume 25 per cent of their calories as sweetened beverages experienced a significant drop in metabolic rate, reported researchers at the University of California, Davis, in the European Journal of Clinical Nutrition in 2012.

GET MOVING AND LIFT WEIGHTS

Lack of exercise also slows your metabolism, numerous studies suggest – as does not getting enough sleep.

When scientists at the University of Pennsylvania asked healthy volunteers to restrict their sleep to only four hours a night for five nights, they found that their metabolic rates fell by 2.5 per cent on average – which was apparently caused by their body clock being disrupted.

The study participants’ metabolic rates returned to their previous level after they had 12 hours of uninterrupted sleep, the journal Obesity reported in 2015.

Another significant factor implicated in slowing average metabolic rates is ageing – as a result of exposure to metabolism-slowing factors, such as disrupted sleep and lack of exercise. As Dr Collins explains: ‘Once you are midlife, your metabolic rate can go down by as much as 10 per cent every decade.

‘Another crucial factor is that as we age we are likely to lose muscle – and muscle plays a crucial role in maintaining our metabolic rates.’

To keep our metabolic rates high in later life – and thus keep weight gain at bay, ‘it’s crucial that we ensure that our muscles are kept working’, he says.

‘It’s particularly important to be doing exercise, particularly weight-bearing exercises, to maintain muscle.’ This is borne out by research by Southern Illinois University in 2009 which showed that fairly minimal exercise regimens – training for 11 minutes per day, three days a week – can raise your metabolic rate by around 7.5 per cent.

The researchers reported that this translated into burning 125 extra calories per day on average – equivalent to a 3oz serving of roasted chicken breast.

Resistance exercise doesn’t have to involve strenuous exertion – gardening and walking are both effective forms, says Dr Collins.

TURN DOWN THE CENTRAL HEATING 

Being too warm might slow your metabolic rate.

Research shows that living in the 12C-17C average winter temperatures found in 1950s homes boosts metabolic rate by one third, reported a 2014 study in the journal Trends in Endocrinology & Metabolism.

If the temperature drop causes shivering, this raises metabolic rate five-fold, to 400 calories per hour. Dr Collins explains: ‘That’s down to a substance in our bodies called brown fat burning up energy to keep us warm.’

Brown fat is heat-producing – it generates 300 times more heat than any other organ in the body.

Babies rely on it to help regulate their body temperatures, and as a calorie-burning furnace it can help us to stay slim.

But most of it can disappear with age, possibly down to our cosily heated modern ways.

You can, however, boost its activity – a study published in the New England Journal of Medicine in 2009 showed that moderately cool temperatures of 16C activated brown fat in 23 out of 24 study volunteers. And this calorie-burning brown fat kicked into action after only ten days in the lower temperatures.

Wouter van Marken Lichtenbelt, a professor of ecological energetics and health at Maastricht University in the Netherlands, who led the research, said we adapt quite quickly to cold.

Furthermore, people who spent six hours at 15C for a period of ten days increasingly felt more comfortable and eventually shivered less.

This would not, however, be suitable for some people, including elderly and vulnerable groups who are advised to keep indoor temperatures at around 18C.

So perhaps returning to some of the habits of the 1950s – before our metabolic rates began to slow down – could significantly help to address the obesity epidemic.