You’d be forgiven for thinking that weight loss is a piece of cake – especially at this time of year when wellness influencers and fitness magazines are flexing their ‘easy-to-follow’ transformation programmes.
Then there are supplement companies, slimming groups, personal trainers and biotech firms, all jostling for a slice of the big weight-loss pie. The industry is projected to be worth over £380bn ($500bn) less than a decade from now.
But here’s the thing that’s rarely acknowledged: weight loss is tremendously difficult – especially for beginners. It’s believed the majority of diets fail, often within weeks, and studies repeatedly show that people who do lose weight usually put it back on – and more – within a couple of years.
In the UK, two-thirds of adults are overweight. In the US, it’s closer to three-quarters. There’s lots of evidence weight loss could improve the quality and quantity of their lives.
In 2025, researchers found that cutting just five per cent of body mass could lead to improved health markers for people with obesity – even if they regain some of the weight – from lower blood pressure and cholesterol to healthier liver function, reduced inflammation and better sleep.
However, a 2025 study in the journal Heart found that weight fluctuations can be dangerous, increasing the risk of death in obese people with cardiovascular issues.
So what’s the answer? Steady, sustainable, successful weight loss, which is about shifting to a healthier overall lifestyle that you can maintain.
We’ve spoken to leading experts and sifted through the latest weight-loss research to identify the strategies that genuinely work. Here are six you can try in the first 100 days of a weight-loss effort to boost your chances of long-term success.
Know your enemy
When it comes to losing weight, the obstacles aren’t limited to ready meals, fizzy drinks or stuttering willpower. Your real opponent is thousands of years of evolution, which have taught our bodies to notice when we start losing weight – and do something to stop it.
“When we have a calorie deficit, our body kind of panics on an evolutionary level,” says Dr Rachel Woods, a physiology researcher at the University of Lincoln.
“There’s evidence to show that when someone starts to lose weight, our body does some annoying things that counteract that.”
These include increasing levels of our hunger hormones and lowering energy expenditure in ways we don’t notice. You might walk around or fidget less, Woods says. “Our bodies get more efficient at burning energy – and our basal metabolic rate decreases.”
These adaptations evolved to help us in periods of scarcity, but they work against us in the modern world. For most of us living in developed countries, energy-dense foods are cheap and plentiful.
“It’s really easy to eat 500 calories,” Woods says. “You could do that in a few minutes if you were hungry and had some chocolate bars or whatever you fancy. But to burn 500 calories is so much harder.”
That’s why, if you want to lose weight and keep it off, then permanent changes in your nutrition and lifestyle are better than a crash diet – because when the diet ends, those energy-dense foods are still just as available.
Rethink your goals
Drastically cut your calorie intake and/or start exercising much more than usual, and you can lose weight quickly, says Woods.
“If, hypothetically, you ate a very low-calorie diet of say 600–800 calories a day, you could expect to lose quite a bit of weight,” she says.
“But realistically, how long can someone sustain that for? We generally recommend people set a target of [losing] about five per cent of their body weight.”
Another way to frame it is to think about where you want to be in three years, rather than three months. Adopt smaller measures that are easier to adapt to and get results over time.
“One approach that often works well is using SMART goals,” says Dr Laura Kudlek, a researcher at Cambridge, who is exploring the psychological factors behind weight loss.
“That is, goals that are Specific, Measurable, Achievable, Relevant and Time-bound. Rather than saying ‘I want to lose weight’, a SMART goal could be ‘I will go for a 15-minute walk after lunch three times this week’.”
Weight loss itself might not be the right measure. If you add muscle while you’re training, your weight won’t fall as quickly, as muscle weighs more than fat.
A shrinking waist circumference, for example, is a good sign you’re losing visceral fat around your internal organs.
Falling blood pressure, lower cholesterol, improved sleep or increased strength at the gym also tell you that whatever you’re doing, it’s working – because your health is improving.
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Start lifting weights
There was a time when exercising to lose weight meant one thing: cardio. Walking, running, cycling and aerobic exercise classes were the standard approach, simply because they can burn a lot of calories.
In recent years, however, researchers have shifted their attention away from the treadmill to the weight-lifting section of the gym.
“If you do resistance training, with weights or using your own body weight, you’re going to be building your muscle mass,” says Woods.
“That means you burn more energy because muscle is very active and it uses a lot of energy. So if you have a higher muscle mass, even when you’re sitting on the sofa, you’ll be burning more energy than if you had a lower muscle mass.”
High-intensity strength training, where you push yourself to the limit, also has a kind of ‘afterburn’ effect. Known as EPOC (excess post-exercise oxygen consumption), the effect leads to an increase in the energy burned for an extended period after your workout ends, as your body works to repair the muscles used.
In a landmark paper from 2002, researchers showed the effect continues for a whole 38 hours after your workout.
Studies also show that people who do resistance training for weight loss regain less weight than people who don’t do it. This is probably because of the long-term increase in their resting metabolic rate.
Weight training can be intimidating for beginners, but the good news is that you don’t have to lift heavy to see results. Research shows that lifting lighter weights for more repetitions can have similar effects as lifting heavy weights for fewer reps.
Don’t neglect other forms of exercise
All movement matters. That’s the general consensus that underlies most recommendations around healthy weight loss.
Aerobic exercise may trigger your hunger hormones, but research shows it can be highly effective at reducing body fat and waist circumference – if you do enough.
A 2024 review into the existing evidence found that you need a minimum of 150 minutes of vigorous exercise, or 300 minutes of moderate exercise, per week to see clinically meaningful weight loss, assuming you’re not also cutting calories from your diet.
It sounds like a lot, and that can be off-putting for some people. However, Prof Adam Collins of the University of Surrey says that another tweak in the way you think about it can be life-changing.
“Basically, this is making you metabolically healthier and fitter,” he says. “So actually, fitness is the key goal, not burning a certain number of calories. Because what also happens as you exercise is your capacity for exercise increases – and that tends to drive more physical activity.”
In other words, the more you exercise, the more you can exercise, and the more you enjoy it. Whether it’s a team sport or orienteering, bodybuilding or gardening, if you find something you enjoy, weight loss becomes less of a chore and more of a by-product of your hobby.
Fuel your exercise
There is a lot of advice out there about how to use nutrition to drive weight loss. Don’t eat late at night. Beware the liquid calories in sauces, sweet drinks and alcohol. Watch your portion sizes. Time your meals to your circadian rhythm. Eat slowly. Chew more.
It can be overwhelming for beginners. The key thing is simply to use more energy than you consume – but also making sure, especially if you’re exercising, that your body has the fuel it needs to make your workouts manageable.
Otherwise, you can lose lean muscle mass and bone density, as well as fat stores, Collins says.
He recommends making sure your diet includes enough protein to “minimise the amount of fat-free mass or body protein that you’re losing, particularly if you’re doing some form of resistance exercise”.
Typical recommended amounts range from 0.8 to 1.6g of protein per kilo of bodyweight, or between 20 and 30 per cent of your daily calories.
“Also think about adding things to your diet,” says Woods. “That sounds a bit counterintuitive, but I like to be able to tell people to increase certain things because diets are usually all about taking stuff away.
“Increasing the amount of plants you eat – so adding lots of vegetables and fruit and nuts – makes you more likely to feel full and less likely to eat more energy-dense foods that might increase your weight.”
Plan for plateaus
Many weight-loss programmes falter at some point. Willpower dips. Life gets in the way. Your metabolic rate slows down. “You’ll also just reach a plateau, when you’re essentially at energy balance again,” says Collins.
Let’s say you’ve lost 10 per cent of your body weight. That’s a great achievement, but because your new, smaller body requires less energy than it used to, you need to cut more calories if you want to lose more weight.
“You either need to sustain the energy balance you’re at to avoid regaining the weight,” Collins says, “or, if you want to carry on losing weight, you need to create another energy deficit.”
You could increase the amount or intensity of the exercise you do because your fitness levels will have improved. You may also choose to improve your diet further.
This can be when things get difficult, Kudlek says. “Weight loss is hard, and maintaining it is even harder. That’s not about willpower, but about biological changes in the body and an environment that promotes unhealthy food.”
Research shows it can take six weeks or more to instil healthy habits in new gym members, so don’t beat yourself up if you’re not there yet.
Kudlek recommends thinking about your weight a bit like your blood pressure. “It often needs ongoing management, rather than a one-time cure,” she says.
“A few things may help during those early months: expecting lapses rather than seeing them as failure; practising mindfulness and how to observe your sensations or cravings; and seeking support early, whether from a programme, clinician or peer group.
“Also, not every programme works equally well for everyone and it may be necessary to try out different approaches before finding a good fit.”
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