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Overweight, Obesity and Weight Loss

This page provides general information about diet-related ill-health. For individual advice, always seek guidance from a qualified health professional. 

What are overweight and obesity?

Healthcare providers use the terms ‘overweight’ and ‘obesity’ to describe an excess of body fat. This can affect both physical and mental health, so managing weight is one way to support overall wellbeing. But this can be hard. While eating healthily and exercising regularly throughout life can help achieve this, our environment often makes it easy to gain weight – and hard to lose it.

 

It’s the amount of fat in the body – and particularly where it’s stored – that affects health rather than weight itself. However, as body fat levels tend to correlate with weight in most people, healthcare providers use weight as a simple way to monitor changes in body fat. Consequently, advice on reducing excess body fat typically focuses on managing weight.

 

There is no ‘quick fix’ for obesity. Weight loss takes time and commitment. However, even losing and keeping off even a small amount of weight can produce health benefits and reduce your risk of developing obesity-related diseases.

 

 

Zoe Hill, Nutrition Scientist, British Nutrition Foundation

What causes overweight and obesity?

Overweight and obesity result from an imbalance between the energy (calories) we take in and the energy our bodies use. In the past, this led to the belief these conditions were simply due to eating too much and exercising too little. However, research now shows managing our weight is far more complex than this and is influenced by many factors. Diet and physical activity certainly play a part, but our genetic make-up has a major role in determining our weight and susceptibility to weight gain.

 

Various health conditions, medications, and factors like stress, anxiety, depression and poor sleep, can also influence weight. Additionally, research shows that experiencing weight stigma can have its own impact on health and weight.

 

The environment we live in plays a major part, too. For example, high streets full of fast-food outlets, advertising of less nutritious foods, and shopping centre layouts that mean escalators are more accessible than stairs, all make it easier to eat less healthily and be less active.

 

Over time, these influences can lead to an excess of energy that’s stored in the body as fat, resulting in gradual weight gain.

 

With so many factors involved, it’s clear that managing weight isn’t just about personal responsibility. The food industry, local councils and government, for example, all have a part to play in making healthy eating and an active lifestyle easier and more accessible for everyone.

Key facts

How are overweight and obesity diagnosed?

There are two methods commonly used to assess weight. These are:

  • Body Mass Index (BMI)
  • Waist to Height Ratio

 

Body Mass Index (BMI)

This considers a person’s weight in relation to their height and is the measurement commonly used in healthcare settings. For most adults:

  • A BMI between 18.5 and 25 is defined as healthy
  • A BMI of over 25 is defined as overweight
  • A BMI of over 30 is defined as obese

 

In people with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, a BMI of 23 is defined as overweight and a BMI of 27.5 as obese. These lower values are due to differences in where fat is distributed in the body, which affects health risk.

 

Though the BMI scale divides weight into specific categories, it’s helpful to remember that weight exists on a continuum. Health risks don’t suddenly appear at a specific BMI number, like 30. Instead, research confirms that as BMI increases, the likelihood of certain health issues may gradually rise, with higher BMIs linked to a greater chance of developing some health problems.

 

You can assess your weight with this BMI calculator.

 

Measuring BMI only measures weight and doesn’t take into consideration the amount of body fat a person has or where it is stored. This means it may be an inaccurate measurement for some – for example, people who are very muscular may have a high BMI without an excess of body fat.

 

Waist-to-Height Ratio

Measuring the waist-to-height ratio gives a better understanding of where fat is stored in the body, and especially whether it’s accumulated around the stomach. This is important because fat stored around the stomach poses a higher health risk than fat stored in other parts of the body. A larger waist may indicate higher amounts of visceral fat, a type of fat that builds up around and inside organs.

 

To measure your waist-to-height ratio…

  1. Measure your waist circumference – wrap a tape measure around your waist midway between the bottom of your ribs and top of your hips. Breathe out naturally then take the measurement in inches or centimetres.
  2. Work out your height in the same units used to measure your waist.
  3. Divide your waist measurement by your height measurement.

 

To interpret the results:

  • A ratio between 0.4 and 0.49 indicates no increased health risk
  • A ratio between 0.5 and 0.59 indicates an increased risk to health
  • A ratio between 0.6 and 0.69 indicates further increased risk to health

 

For example, if your waist measurement is 94cm (37in) and your height is 168cm (5ft 6in or 66in), the calculation would be 94 divided by 168 (or 37 divided by 66), giving a value of 0.56, indicating an increased risk to health.

How do overweight and obesity affect health?

A higher BMI or waist-to-height ratio doesn’t automatically mean a person will experience health problems.

 

These measurements don’t consider other important factors that affect health such as physical activity, sleep quality, the types of food eaten, alcohol intake, smoking habits or stress levels.

 

However, there’s good evidence that higher BMIs and waist-to-height ratios are linked to a greater likelihood of certain health conditions.

 

Health organisations, including the NHS, note that living with overweight and obesity may increase the risk of…

  • Type 2 diabetes
  • High blood pressure
  • High cholesterol
  • Coronary heart disease and stroke
  • Certain cancers, including breast, bowel, and womb cancer
  • Metabolic syndrome, a combination of type 2 diabetes, high blood pressure and obesity
  • Asthma
  • Gallstones
  • Osteoarthritis
  • Liver and kidney disease

 

Living with overweight and obesity may also contribute to mental health conditions such as depression, affect fertility, and increase the risk of pregnancy complications such as gestational diabetes and pre-eclampsia (high blood pressure during pregnancy).

 

It can be hard to find the motivation to lose weight to protect our long-term health, especially if we’re not currently experiencing any health issues. But managing our weight also brings other benefits that may have a positive impact on our everyday wellbeing such as:

 

It’s worth noting we don’t need to reach a BMI within the healthy range for health to benefit. In particular, losing 5-10% of weight is consistently found to improve health, although studies show even smaller amounts than this can still be beneficial. This is what 5-10% weight loss looks like for different weights…

 

If you weigh…

A 5% weight loss is…

A 10% weight loss is

70kg (11st)

3.5kg (8lb)

7kg (15lb)

80kg (12st 8lb)

4kg (9lb)

8kg (18lb)

90kg (14st 2lb)

4.5kg (10lb)

9kg (20lb)

100kg (15st 10lb)

5kg (11lb)

10kg (22lb)

110kg (17st 5lb)

5.5kg (12lb)

11kg (24lb)

120kg (18st 13lb)

6kg (13lb)

12kg (26lb)

How do I lose weight?

Our weight is influenced by the balance between the energy (calories) we take in from food and drink, and the energy we use through daily activities and exercise. When our energy intake matches the energy we use, our weight stays stable. If we regularly take in more energy than we use, the extra is stored as fat, leading to weight gain.

 

To lose weight, we need to create an energy or calorie deficit by using up more energy than we take in, so our body relies on its fat stores for fuel. This can be achieved by modifying our diet to reduce calorie intake, being more physically active to increase calories used, or a combination of both.

 

While the idea of creating a calorie deficit might sound simple, it can be far more challenging in practise. Our modern environment makes it easy to eat high-calorie foods and be less active. This means it takes effort to change our behaviour, so we make healthier food choices and incorporate more activity into daily life.

 

Evidence suggests that combining diet, physical activity and support to change behaviour is the most effective approach for weight loss. The NHS does this with its free 12-week online weight-loss plan that includes diet and exercise advice, a weight-loss forum and email support. Find out more on the NHS website.

Diet

It’s generally easier to create a calorie deficit through diet than exercise, so advice often focuses on helping people manage what they eat and drink. This often takes the form of a structured weight loss plan or diet that reduces overall calorie intake.

10 simple tips to support weight loss

  1. Plan meals and write shopping lists so you have all the ingredients you need to make dishes – you’ll be more focussed in the supermarket and less tempted to grab processed meals, fast food or takeaways.
  2. Eat more vegetables and fruit – have at least five servings a day and vary your choices to keep meals interesting and boost the range of vitamins and minerals in your diet.
  3. Swap some meat for budget-friendly plants – turn some favourite meals such as chilli, lasagne or curries into veggie options or replace some of the meat with beans, lentils, chickpeas or tofu, e.g. use less mince and more beans in a chilli. Plant foods are lower in calories and fat than meat but many, such as pulses, are still high in protein. Plus, they contain fibre to help fill us up!
  4. Bake, boil, steam, grill, poach, air fry or microwave food rather than frying – all oils are very high in calories so use small amounts, if any.
  5. Go for suitable portion sizes – it can be difficult to judge how much food to serve. Use the portion size guide to help work out how much to put on your plate.
  6. Choose reduced-fat dairy products such as skimmed or semi-skimmed milk, reduced-fat cheese and low-fat yogurt, and only use small amounts of spreads.
  7. Go for darker coloured carbs – swap white pasta, rice, noodles and bread for the brown varieties. They’re more filling thanks to the extra fibre they contain.
  8. Don’t drink your calories – quench thirst with water or calorie-free drinks. It’s also sensible to limit alcoholic drinks as they’re packed with calories but often add no nutrients to diets.
  9. Eat fewer fatty and sugary snacks like crisps, chocolates, cakes and biscuits – think of them as occasional treats that you can enjoy in small quantities, rather than foods you eat every day.
  10. Read nutrition information on food labels and choose foods with fewer calories – traffic light colours on the front of packaging also shows whether a product has a high (red), medium (amber) or low (green) amount of fat, saturates, sugars and salt – choose products with fewer reds.

Which diets work?

With so many weight loss plans available, choosing one can feel overwhelming. It’s important to remember there’s no perfect plan – different approaches will be successful for different people. Finding a plan that fits into your lifestyle, matches your food preferences, and suits your budget is key, as being able to stick to a plan is what truly supports success.

 

A good starting point is to choose a plan based on the principles of healthy eating. This provides a solid foundation for long-term eating habits, benefits overall health beyond weight loss, and encourages a healthy relationship with food.

 

To support weight loss, it’s important to combine these principles with calorie and portion control.

For a steady weight loss, aiming for a deficit of 600 calories a day is advised. This means consuming around 1,400 calories a day for women, and around 1,900 calories a day for men. For many, this results in a weight loss of around 0.5kg (1lb) a week, although this varies based on many factors, including the amount of exercise taken.

 

The following chart summarises weight loss diets that have evidence to support their effectiveness. Children, teenagers, pregnant and breastfeeding women, those with medical conditions or taking medications, and anyone with a history of eating disorders should consult a healthcare professional before starting any weight loss plan.

Calorie Counting

How it works:

A daily calorie allowance is set to create a calorie deficit. A person sticks to this allowance by calculating the calories in the food and drink they consume.

Benefits:
  • Effective for creating a calorie deficit
  • No foods are off limits
  • Calorie information is available on all food labels
  • Helps to limit foods high in fat and/or sugar, and low in nutrients e.g. biscuits, chocolate, crisps, chips, cake
  • May suit those who prefer structured advice
Factors to consider:
  • Counting calories can be time consuming and challenging to maintain long term
  • Can become obsessive, potentially creating an unhealthy relationship with food
  • Calories don’t reflect the nutritional quality or how filling a food is

Low Fat

How it works:

Low-fat diets limit high-fat foods, which reduces calories. Fat provides twice as many calories as protein or carbohydrate.

Benefits:
  • Studies show low-fat diets are effective for weight loss
  • Many low-fat products are available, and labels make it easy to identify them
  • Helps reduce saturated fat, which benefits cholesterol and heart health
Factors to consider:
  • Should still limit sugar, refined carbohydrates and processed foods
  • It’s important to include some nutrient-rich high-fat foods for essential fats e.g. a portion of oily fish a week
  • Diets may be less filling, potentially affecting hunger and satisfaction – including high protein and high fibre foods can help.

Carb Restricted

How it works:

Carbohydrate intake is restricted, which lowers calories. Low-carb diets allow around 50-130g carbs a day; very low carb diets like keto limit to under 50g carbs a day (see Frequently Asked Questions).

Benefits:
  • Limits food that are also high in fat or salt, and low in nutrients e.g. biscuits, chocolate, crisps, chips, pastries and cake
  • Studies confirm low-carb diets are effective for weight loss (although not superior to other diets)
  • May improve blood sugar control for some with type 2 diabetes
Factors to consider:
  • Can be low in fibre leading to constipation, so including some fruit, veg and wholegrains is essential
  • It’s important to avoid high saturated fat intake
  • Initial side effects may include headaches, low energy, dizziness, nausea, bad breath, though these normally ease
  • While very low carb diets may support weight loss, more research is needed to assess their long-term health impacts

Slimming Clubs

How it works:

Clubs like Slimming World and Weight Watchers offer reduced-calorie plans based on points or scoring systems plus weekly group meetings. Online programmes such as Second Nature and Oviva are also available.

Benefits:
  • Plans are based on healthy eating guidelines and limit fatty, sugary and calorie-rich foods but still allow favourites
  • Group support can boost motivation and help people stay on track
  • Provide support materials and recipes
  • Weight maintenance support is provided
  • Some healthcare providers may provide free access to clubs
Factors to consider:
  • Group sessions may not suit everyone or fit into personal schedules
  • Weekly weigh-ins may be stressful or discouraging, especially if weight loss stalls
  • Membership fees may be costly
  • Group discussions may cover topics not relevant to everyone’s goal or interests

Time-restricted eating

How it works:

Also called intermittent fasting, this method alternates normal eating with fasting to create a calorie deficit. Types of plan include the 5:2 diet (normal eating for 5 days, restricted for 2 days) and 16:8 diet (eating within an 8-hour period each day).

Benefits:
  • Studies indicate restricted eating can be effective (although no more so than other plans)
  • May help reconnect with hunger and fullness cues
  • Can help break habits like overeating or constant snacking
  • Appealing to those who like the idea of a ‘part-time’ diet
Factors to consider:
  • Unsuitable for anyone with a history of eating disorders or mental health conditions
  • Extended fasting periods may reduce the effectiveness of some medications, so this isn’t suitable for individuals on certain medications
  • Fasting periods can result in extreme hunger, which may lead to overeating during eating periods.
  • It’s vital to avoid ‘feasting’ and to eat healthily around fasting periods

Total Diet Replacement (TDR)

How it works:

Replaces meals and snacks with specially formulated shakes, soups or bars. Sometimes called ‘Soup and Shake’ diets, they provide around 800-1200 calories a day creating a large calorie deficit. Some plans (Partial Diet Replacement) replace one or two meals a day so create a smaller calorie deficit.

Benefits:
  • Allows for rapid weight loss, which can be very motivating
  • Good evidence suggests for some, they can put type 2 diabetes into remission
  • Soups, shakes and bars supply all the nutrients needed to support good health
  • Products remove the need to think about what to buy, cook or eat
  • May be available on prescription from healthcare providers as part of a weight management programme
Factors to consider:
  • Plans should be followed with medical and behavioural support to ensure safety and long-term effectiveness
  • Only recommended for 12 weeks
  • Unsuitable for those with a history of eating disorders, certain medical conditions or some medications
  • Some may experience hunger, low energy, headaches, dizziness and nausea, especially initially
  • They don’t allow for eating socially
  • Sticking to soups, shakes and bars can be monotonous
  • Food needs to be reintroduced gradually and supported with advice from health professionals to maintain health and long-term success

How to spot a fad diet

Diets promising quick and easy weight loss may be tempting but they’re ineffective in the long term and may harm health.

 

Many fad diets involve severely restricting food intake, leading to poor nutrition, low energy levels, dizziness, nausea, headaches and weakness. They may also cause extreme hunger, which can trigger cravings.

 

Succumbing to these cravings may lead to feeling guilty, out of control or a failure, sometimes prompting further attempts to restrict food. This cycle of starving and overeating can lead to an unhealthy relationship with food, and over time may harm both physical and mental health.

As a rule, if a diet sounds too good to be true, it probably is! The following are all signs a diet may be a fad

  1. Promises fast weight loss – while fast weight loss might be recommended in specific cases, for example, to put type 2 diabetes into remission for some, this should always be done with medical supervision. Gradual, steady weight loss is safer and more likely to be maintained.
  2. Eliminates or demonises whole food groups or certain foods – unless there’s a medical condition that demands it, there’s no reason to eliminate any food.
  3. Promotes eating foods in certain combinations – there’s no scientific evidence to support this. Our bodies are naturally equipped to digest a balanced, mixed diet.
  4. Recommends eating large amounts of one type of food – diets like this are unlikely to be balanced.
  5. Offers a quick fix or suggests weight loss will occur without the need to make changes to eating habits – sustainable weight loss requires a shift in diet and exercise patterns.
  6. Promotes ‘miracle’ foods – there are no magic foods or drinks that result in weight loss.
  7. Lacks scientific support – personal stories or testimonials aren’t a substitute for research. Reliable diets are backed by credible studies, not isolated or small-scale research.
  8. Supports the idea of detoxing or cleansing – our bodies naturally detoxify, and extreme diets focusing only on fruit, vegetables, or water will lack nutrients needed for health.
  9. Recommends purchasing supplements or special products – in most cases weight loss and good nutrition can be achieved through a balanced diet and being more active so there is no need for expensive products. To find out more about supplements and when they may be needed, see our page on vitamins and minerals.

Physical activity

Though physical activity alone tends not to lead to significant weight loss for many people, it’s still an essential part of weight management as it helps to prevent weight gain and makes it easier to maintain weight loss over time. Plus, being active has many other health benefits, including preventing stroke, heart disease, high blood pressure, osteoarthritis, lower back pain, type 2 diabetes, some cancers, depression, anxiety and dementia.

 

If you’re not currently active, start to increase the amount you do gradually by sitting less, standing more and incorporating small changes like using stairs instead of escalators or walking short distances rather than driving.

 

Then aim to build up to at least 150 minutes of moderate-intensity activity each week. This should be spread out over at least four to five days such as 30 minutes a day, five times a week. Exercise that’s moderately intense should make you breath faster, feel warmer and increase your heart rate, and includes activities such as brisk walking, cycling, dancing or gardening.

 

It’s also important to do muscle-strengthening activities at least twice a week. Examples include yoga, pilates, lifting weights or bodyweight exercises such as sit ups and push ups.

 

As fitness increases, it’s beneficial to increase the amount and intensity of physical activity done. To prevent weight gain, most people need to do 45 to 60 minutes of moderate intensity activity each day – and for those who have lost weight, they may need to up their activity to 60 to 90 minutes daily.

 

The NHS website provides plenty of resources on physical activity, including advice on walking for health, exercise guidelines, and the Couch to 5k programme.

5 tips to increase physical activity

  1. Add ‘movement breaks’ into your day – stand up, stretch or do a few squats every hour if you spend a lot of time seated. Use reminders or apps to prompt you to take movement breaks.
  2. Build physical activity into your daily routine, such as walking to work, taking the stairs instead of the lift, or parking further away from the supermarket entrance.
  3. Set realistic exercise goals – you don’t need to sign up for a marathon to improve your fitness! Aim for manageable goals that fit into your lifestyle, such as doing a 15-minute workout at home or taking the dog for a walk.
  4. Find an activity you enjoy – this could be joining a dance class, gardening, or playing a team sport. The more you enjoy it, the more you are likely to do.
  5. Make exercise social – turn social events into opportunities to get active. Instead of meeting in a pub or restaurant, arrange to go 10-pin bowling, go for a swim and sauna, or enjoy a walk in the park.

 

For more tips on increasing your physical activity read our page on activity in daily life.

Behaviour change

Research shows that working on behaviour changes alongside diet and physical activity can help to support weight loss. For some, counselling or therapies such as cognitive behavioural therapy (CBT) may be helpful. Other supportive activities include:

  • Setting realistic goals
  • Keeping a food and exercise diary
  • Tracking progress
  • Identifying triggers for unhealthy eating habits
  • Finding techniques to manage and prevent setbacks
  • Practising mindful eating
  • Getting support from friends, family, online weight-loss communities, local slimming clubs, or healthcare professionals

 

Other weight loss options

Some people may benefit from medication or surgery to support weight loss, especially if attempts to lose weight through making changes to diet and exercise haven’t had a significant impact. These treatments are intended for those with higher BMIs and related health issues and may not be suitable for everyone. To learn more, check the NHS website or speak to your GP.

 

Weight loss medicines

It’s vital that weight loss medications are accessed through medically qualified healthcare professionals and not bought online. The following are currently available to people living with obesity or overweight along with a condition such as type 2 diabetes on the NHS

 

  • Pills: Orlistat (Xenical) works by reducing fat absorption (and therefore calories) by around one third. It’s available by prescription or in a lower dose from pharmacies, with pharmacist supervision.
  • Injections: Semaglutide (Wegovy) and Liraglutide (Saxenda) work by slowing food movement in the gut, which reduces appetite, increases feelings of fullness and helps control blood sugar (glucose) levels. Available by prescription, semaglutide is injected weekly, and liraglutide daily.A new weekly injection –  Tirzepatide (Mounjaro) – has also recently been approved for use in the UK and works in a similar way to semaglutide and liraglutide. Ozempic is another brand of semaglutide but it’s only approved to treat type 2 diabetes in the UK not weight loss.

 

Weight loss drugs may also be available through private prescription for those who are eligible.

 

Weight loss surgery

Also called bariatric surgery, this option may be available through the NHS for some people with a very high BMI. Procedures include gastric bypass, gastric band, gastric balloon and sleeve gastrectomy, all of which make the stomach smaller, to help people feel fuller faster and eat less. Find more information about weight loss surgery on the NHS website.

Frequently asked questions

If you’re concerned about your child’s weight, seek advice from a health professional who can offer guidance tailored to their age, growth, and nutrition needs. Additional information about children’s weight and healthy growth can also be found on the NHS website.

There’s evidence a vegan diet may support weight loss, largely because replacing animal products like meat and dairy with plant foods can help lower calorie and fat intake. Vegan diets also tend to be higher in fibre, which can promote fullness and reduce hunger. However, switching to a vegan diet doesn’t guarantee weight loss. Vegan diets can still be high in calories, saturated fat, sugar and/or salt, especially if they include large amounts of vegan chocolate, biscuits, cakes, fried food, pastry products and takeaways.

Whether you eat meat or follow a vegan diet, it’s important to follow healthy eating guidelines and, for weight loss, to create a calorie deficit.

A traditional Mediterranean diet includes plenty of vegetables, fruits, wholegrains, pulses, oily fish, nuts, seeds, and olive oil, along with some dairy products, poultry, and eggs, and limited red meat, butter, sugar, and processed foods.

As it’s largely plant based, a Mediterranean diet can be rich in fibre, which some research has shown to promote fullness and reduce hunger. Studies suggest this type of diet may support weight loss, especially if calories are reduced. To achieve this, it’s important to monitor portion sizes and enjoy calorie-rich foods such as nuts, seeds and olive oil in small amounts.

The keto diet restricts carbohydrate intake to around 20-50g a day and typically includes higher amounts of fat and moderate protein. This usually leads to a lower calorie intake and may enhance weight loss by encouraging the body to use fat as its main energy source. This fat-burning process produces substances called ketones, which provide fuel for the brain and may help to reduce appetite, although more research is needed to confirm this.

While studies suggest keto diets result in weight loss, there’s insufficient evidence to conclude they’re more effective than other traditional weight loss methods over the long term. Plus, more research is needed to assess the long-term safety and health impacts of keto diets, particularly in relation to heart health.

Slow, steady weight loss – around 0.5-1kg (1-2lb) a week – is typically recommended by health professionals. However, rapid weight loss may be beneficial in certain circumstances such as in preparation for surgery or before fertility treatment.

Rapidly losing a large amount of weight can also be an effective way to put type 2 diabetes into remission in some people with a higher BMI. It’s always best to consult a healthcare professional before pursuing rapid weight loss though, as this should be done with medical supervision to ensure diets are adequate.

Losing weight to the point of becoming underweight can lead to health issues. Eating disorders can affect boys, girls, men, and women from all backgrounds and ethnic groups, including people who have attempted to lose weight. You can find more information and support for disordered eating on the Beat website.

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Please note that advice provided on our website about nutrition and health is general in nature. We do not provide any individualised advice on prevention, treatment and management for patients or their family members.