Intermittent fasting or high protein, which diets are worth it? Read on to find out.
Search for “diet books” on Amazon and there are more than 100,000 results, and the hashtag #WeightLossDiet gets a massive 250 million on TikTok. So where do you start?
The benefits of following a healthy diet
“Health professionals recommend that weight-loss plans are based on healthy-eating principles,” says registered dietitian Sian Porter, a spokeswoman and fellow of the British Dietetic Association. “Together with having a healthy relationship with food, this provides a long-term framework and health benefits that go beyond waistlines.”
But it’s important to take a flexible and individual approach, a point made by the National Institute for Health and Care Excellence in its weight management guidance.
“These days, health professionals advise on all sorts of weight-loss plans, including diets they may traditionally have questioned in the past, such as carb-restricted diets, meal replacements or referrals to slimming clubs,” confirms Porter. “It’s about finding what works for you while looking after your health in the short and long term. But fundamentally, the principles of a healthy, balanced diet, including the amount, type and frequency of food and drink you consume, should underpin all weight-loss plans,” she adds.
The priority, say doctors, is helping those who are overweight or obese manage their weight so that they can enjoy better health. “Of course, good health is far more than just a number on the scales,” says Dr Dawn Harper, an NHS GP and the author of Dr Dawn’s Guide to Weight & Diabetes. “Living with obesity increases the risk of health problems, including type 2 diabetes, heart disease and many cancers. Plus, it can affect mental well-being and exacerbate symptoms linked to other conditions such as asthma and arthritis.”
There’s no need to reach an ideal weight range for health to improve either. “Research shows that losing just 5 per cent of body weight is beneficial. For someone weighing 80kg, that’s equal to losing 4kg,” says Dr Harper.
How to get started with a diet that really works
The starting point for getting our body into shape begins with our mind. That means ditching a “diet” mentality, believes psychologist and therapist Emma Kenny, who counsels clients on weight management. She says: “Embarking on a dietary journey requires cultivating a nurturing mindset, reframing our perspective from one of restriction to one of nourishment and self-care.”
Establishing realistic goals is important. “Begin by setting achievable, specific and time-bound goals,” says Kenny. Rather than aiming for rapid and unsustainable weight loss, she says the focus should be on fostering lasting habits. “Instead of viewing dietary changes as temporary, reframe them as positive lifestyle adjustments made for long-lasting health and wellbeing.”
What about when the going gets tough? “Navigating dietary changes necessitates managing expectations and embracing patience,” explains Kenny. “Acknowledge that challenges and setbacks are inherent to any journey and utilise them as learning opportunities to foster resilience and maintain progress. If a setback occurs, view it as an isolated incident rather than a derailment of your entire journey.”
The diets to ditch
Many of us look for the “magic bullet” to achieve our goals, but the reality is that most diets are likely to have elements you like and some you don’t. “It’s about finding what’s right for you,” explains Dr Adrian Brown, a registered dietitian and the chair of the British Dietetic Association’s Obesity Specialist Group. “The best plan to help you successfully lose weight and improve health is one that fits around your lifestyle, matches your food preferences and budget, and results in a change in eating habits you can stick with long term.”
Quick fixes aren’t the solution, agrees Sian Porter. “There are hundreds of weight-loss diets that claim maximum results for minimum effort but there is no miracle solution,” she says. According to Porter, red flags to look for include diets that promote rapid weight loss, recommend removing or avoiding whole food groups such as carbohydrates, push “miracle” foods, or endorse food supplements only.
“Watch out for diets that suggest you don’t need to change your eating habits,” advises Porter. “Plans based only on personal success stories, testimonials, a ‘diet secret’ or a single study won’t be evidence-based either so should be avoided.”
“Meanwhile, there’s one thing all weight-loss plans have in common, regardless of how sensible, well-researched or wild and wacky they are,” says Porter. “You’ll consume less energy [calories] than you’re using up.”
There’s also help available. “If you wish to lose weight and maintain it, having support is key,” says Dr Brown. “Speak with your GP or practice nurse to see what’s available locally and ask if you can be referred to a specialist dietitian to give you the best chance of success.”
So what are the most popular and effective diets that avoid the fads and are grounded in science?
1. The Mediterranean diet
Centred around foods eaten in countries bordering the Mediterranean Sea, a traditional Med diet is plant-based, so rich in fruit, vegetables, wholegrains, pulses, nuts, seeds, olive oil, herbs and garlic. Moderate amounts of seafood, dairy products, poultry and eggs are included; red meat, butter, refined grains and sugary and processed foods are limited.
How the Mediterranean diet works
Though higher in fat, which may seem counterintuitive for weight management, Med diets are usually high in fibre, which improves satiety and reduces hunger, resulting in lower energy intakes. Indeed, a review of studies found that a Mediterranean diet was linked to a 9 per cent reduced risk of obesity or being overweight, and less weight gain over five years. “Evidence shows that people who follow a Mediterranean-style diet can successfully lose weight,” confirms Dr Brown. But calories still need to be restricted for weight loss.
Health benefits of the Mediterranean diet
“Mediterranean-style diets have been shown to reduce the risk of heart disease and stroke,” says Dr Brown. The British Heart Foundation confirms that these diets can protect against high blood pressure, high cholesterol and Type 2 diabetes, key risk factors for heart disease. It’s because they replace cholesterol-raising saturated fats with artery-friendly monounsaturated fats, include omega-3 fats from seafood, and contain more fibre and heart-healthy phytochemicals such as flavonoids. Med diets also support brain health, protecting against dementia, cognitive decline and low mood.
Is it worth a try?
A Mediterranean diet will suit anyone wanting a healthy, and especially a heart-friendly, diet. But be aware of portion sizes. Olive oil, nuts and seeds are high in calories so should be eaten in small amounts for weight loss.
2. The plant-based diet
As the name suggests, plant foods – fruit, vegetables, pulses, wholegrains, nuts, seeds and oils – take centre stage. Though “plant-based” and “vegan” are used synonymously, they’re not the same. Like flexitarian or flexi diets, plant-based diets can still include meat, poultry, fish, eggs and dairy products, just in small amounts.
How a plant-based diet works
“Plant-based diets are shown to be successful at achieving weight loss in people who are overweight or living with obesity,” confirms Dr Brown. The combination of fibre and fluid in plant foods like fruit, veg, pulses and potatoes means they have a low energy density, which research shows can significantly reduce calories. This allows larger amounts to be eaten for fewer calories, which is good as food quantity is as important as food quality for feeling satisfied – for example, for 100 calories you can eat 100g cooked lentils or 720g tomatoes (around eight), but just 44g grilled sirloin steak or 57g roast chicken.
Health benefits of plant-based diets
These diets follow healthy eating guidelines, so they can protect against major diseases like heart disease, stroke, type 2 diabetes and cancer. They’re also better for the planet. According to a University of Oxford study, if everyone adopted global healthy eating guidelines (essentially plant-based diets) by 2050, 5.1 million deaths would be prevented and food-related greenhouse gas emissions would drop by 29 per cent. The key to achieving this though is to ensure diets are mostly based on vegetables, fruit, grains, pulses, nuts and seeds, rather than full of plant-based ultra-processed foods, which can be high in fat, sugar and salt.
Is it worth a try?
The low energy density of plant-based diets allows larger portions for fewer calories, so they may suit people with bigger appetites.
3. The vegan diet
With #vegan getting 129 million hits on Instagram and 38 billion on TikTok, there’s no bigger diet trend right now.
How vegan diets work
Vegan diets exclude all animal products, including meat, fish, eggs, dairy and even honey. They’re not traditionally designed for weight loss. However, like Mediterranean and plant-based diets, replacing meat with plant proteins can reduce calories, resulting in weight loss. For example, per 100g, beef mince contains 255 calories, tofu 73 calories, and chickpeas 129 calories. Danish scientists found vegan diets reduced weight by an average of 4.1kg (9lb), compared with other diets, in adults who are overweight or living with Type 2 diabetes.
Health benefits of vegan diets
Vegan diets can be lower in saturated fat, sugar and salt, and higher in fibre than meat-containing diets. Indeed, there’s evidence they may benefit heart health and protect against cancer, but may be less beneficial for our bones, possibly due to lower calcium and vitamin D intakes. Choosing products fortified with these nutrients – plus vitamin B12 and iodine, which are often lower in vegan diets – helps ensure nutrient needs are met.
Is it worth a try?
Vegan diets can be the next step for people already eating a mainly plant-based diet. It’s important to follow healthy eating guidelines though and avoid relying on processed vegan foods that can be high in calories, saturates, sugar and salt. “If you plan to follow a vegan diet, it’s important to ensure it’s nutritionally balanced and your plate looks like a rainbow [with a variety of brightly coloured foods],” confirms Dr Brown. Peri- and post-menopausal women following a vegan diet should pay particular attention to calcium to protect bones.
4. Atkins and other carb-restricted diets
Diets that restrict carbohydrates have come under many guises over the decades, including Atkins, paleo, Dukan, South Beach and, most recently, keto. While most health professionals don’t advocate extreme carbohydrate restrictions, especially if coupled with very high fat or protein intakes, in recent years there’s been an attitude shift towards lower-carb diets.
How does a carb-restricted diet work?
As the name suggests, carb-rich foods – for example, potatoes, pasta, rice, bread, cereals, biscuits and pizza – are restricted, which reduces calories. UK health guidelines recommend 260g carbs a day but the Scientific Advisory Committee on Nutrition and Diabetes UK confirm diets containing 50-130g carbohydrate a day, followed for up to six months, support weight loss. “Weight loss tends to be greater in the first six months compared to traditional diets. However, at 12 months there’s no difference. This means low-carbohydrate diets aren’t superior to other diets, but they can be very successful,” says Dr Brown.
Health benefits of carb-restricted diets
“Following a low-carbohydrate diet has been shown to facilitate significant weight loss and improve diabetes control in people with type 2 diabetes,” says Dr Brown. There’s insufficient evidence to recommend lower-carb diets to people with type 1 diabetes though. Diets that restrict carbs to less than 50g a day, for example keto or Atkins, do result in weight loss, but more research is needed to assess the health impact. Low-carb intakes typically go hand-in-hand with high amounts of protein, which make them unsuitable for people with kidney problems. Plus, they’re usually high in fat, especially saturated fats, high intakes of which raise cholesterol, increasing the risk of heart disease.
Is it worth a try?
Carb-restricted diets may be helpful for people living with obesity who are at risk of developing, or have already been diagnosed with, type 2 diabetes. Diets should still include fruit, vegetables, some wholegrains or higher-fibre foods, and with limited saturated fat. This will help prevent low energy, constipation, bad breath, headaches and dizziness sometimes seen with extreme carb restrictions (that is, below 50g a day).
5. The intermittent fasting diet
Intermittent fasting intersperses periods of normal eating with periods of food restriction. Plans come in many guises, including 5:2, alternate day, and time-restricted eating, such as 16:8.
How intermittent fasting works
It’s part-time dieting! During fasting periods, little or nothing is eaten and energy intakes plummet. When combined with periods of normal eating, there’s an overall energy deficit that results in weight loss. For example, the 5:2 diet recommends five days of normal eating (around 1,900 calories a day for women) and two days of restricted eating (500 calories a day for women). That’s a total of 10,500 calories over a week, rather than 13,300 calories a week on a normal diet for women, resulting in weight loss.
What are the health benefits of intermittent fasting?
“Evidence shows that intermittent fasting and time-restricted eating can help people lose significant amounts of weight and improve metabolic health,” says Dr Brown. They’re not superior to other plans though. “When compared with other energy-restricted diets at 12 months, there’s no difference in outcomes,” he says.
Plans with fasting periods may help some reconnect with physical signals that tell us we’re hungry and full, and break patterns of grazing and overeating. On the other hand, there’s always the danger that we overcompensate for the lack of food during fasting by eating larger amounts – and more calories – than normal during non-fasting hours.
Is it worth a try?
As food can be restricted for many hours, intermittent fasting is not suitable for people with a history of eating disorders, mental health issues such as depression due to blood sugar swings that affect mood, and anyone on medication, as severely restricting food can affect the efficacy of some drugs. Avoid this diet if you struggle to function when hungry, too.
6. The slimming club diet
Slimming clubs such as Slimming World and WeightWatchers remain popular, with 27.6 and 10.1 million hashtag hits, respectively, on Instagram. Clubs offer online services, although face-to-face meetings are still widespread. Slimming World, for example, has 13,000 weekly groups and 700,000 members across the UK and Ireland.
How do slimming club diets work?
Slimming clubs provide their own reduced-calorie diet plans, usually based on healthy eating and limiting fatty, sugary and calorie-rich foods, although no foods are restricted. Clubs offer weekly meetings with weigh-ins and a group talk, plus support materials such as recipes. “Commercial programmes have been shown to be very successful at helping people achieve significant weight loss and improved health, with some of these benefits being linked to the group support offered,” says Dr Brown.
Health benefits of slimming club diets
The UK’s NHS recognises the role slimming clubs can play in helping people lose weight and works with external organisations such as Slimming World and WeightWatchers, and online providers such as Second Nature, Roczen and Oviva. As these diets are based on healthy eating, they promote good long-term eating habits, while group support provides encouragement and motivation.
Is it worth a try?
Slimming clubs are suitable for most people and offer a weight maintenance programme. But there’s the financial cost to consider.
7. The high-protein diet
High-protein plans often go hand-in-hand with low-carb diets, but are also recognised for weight loss in their own right. There’s no specific diet or amount of protein recommended, although advice often focuses on having 25-30g protein in each meal. A 125g grilled chicken breast contains 40g.
How does a high-protein diet work?
“Protein has been shown to help people feel full,” explains Dr Brown. Protein works its magic by reducing levels of the hunger hormone ghrelin, while stimulating satiety hormones such as cholecystokinin. “High-protein diets can also help to limit muscle mass loss,” adds Dr Brown. This is important as more muscle means a faster metabolism, so we burn more calories, even at rest. Plus, we use more energy to digest and utilise protein than we do for carbs or fat. Dr Brown summarises: “The evidence shows that high-protein diets can help people lose weight.”
Health benefits of high-protein diets
Combining adequate protein with strength training helps protect against the natural loss of muscle mass that starts in our 30s and results in drops of up to 8 per cent every decade – even more once we’re in our 60s. Protein is also an essential nutrient for maintaining healthy bones. It’s important to make sure diets remain balanced though. High protein intakes are often accompanied by a low amount of carbs, and this may cause constipation due to a lack of fibre, negatively affecting our gut microbiome. High-protein diets are also unsuitable for people with kidney problems.
Is it worth a try?
High-protein diets may appeal to fitness fans and be beneficial in mid-life for protecting against the natural decline that occurs in muscle and bone strength. For good health, choose protein-rich foods that are lower in saturated fat, such as lean meat, chicken, fish, pulses, soya products, nuts and seeds.
8. The low-fat diet
These diets became popular in the 1980s, but fell out of favour when it became clear that low-fat intakes were often replaced with large amounts of refined carbohydrates and research started to reveal the importance of “healthy” fats. Modern-day low-fat diets focus on natural low-fat foods and limit processed carbs.
How does a low-fat diet work?
The theory is simple: fat provides twice as many calories as protein or carbs, so eating fewer high-fat foods – such as butter, oil, fatty meat, cheese, full-fat milk and fried foods – reduces calories. “With fat having 9 calories per gram, reducing intake can easily help reduce your overall energy intake,’ explains Dr Brown. Any food with less than 3g fat per 100g is considered low-fat. Food labelling makes it easy to create your own plan.
Health benefits of a low-fat diet
“The low-fat diet is the most studied diet for weight loss and has been shown to help people lose clinically significant amounts of weight and improve their health,” confirms Dr Brown. Low-fat diets mean less saturated fat, a positive move for heart health as high intakes can increase “bad” or LDL cholesterol, which is associated with one in four UK deaths from heart and circulatory diseases.
Low-fat diets typically include less red meat, too, helping reduce the risk of bowel cancer. Health guidelines recommend limiting red meat to 500g (cooked weight) weekly for this reason. Dramatically limiting fat, though, can mean diets lack essential fats that support growth. Plus, fat helps the body absorb many nutrients, including vitamins A, D, E and K.
Is it worth a try?
A low-fat diet is a good choice for anyone who wants to improve their cardio health, but you need to include one serving of oily fish like salmon and mackerel a week – they’re rich in omega-3 fats, which help keep our heart healthy and are vital for brain and eye function. The Scientific Advisory Committee on Nutrition confirms too much saturated fat is bad for heart health and needs limiting.