The healthiest way to lose weight is neither crash diets nor bursts of exercise. The body likes slow changes in terms of food and exercise. For example, someone who hasn't exercised for years shouldn't rush into running miles a day or pounding the treadmill. Not only will the struggle likely leave you feeling disheartened and demotivated, you're also far more likely to injure yourself and set your fitness levels back further.

The same goes for people who suddenly start depriving themselves. Diets that severely restrict calories or certain foods can lead you to be deficient in the nutrients and vitamins that your body needs. Evidence often shows that once you inevitably give up on your new 'diet', you then often regain the weight and possibly more when going back to old ways.

This is not to say that if you need to lose weight you shouldn't do so, but it is important to do it the right way. So, what should you do?

Energy needs and weight loss

Your body uses food for energy. It stores any excess energy as fat. This means if you eat more food than your body needs for daily activities and cell maintenance, you'll gain weight.

To lose weight, you need to get your body to use up these stores of fat. The most effective way to do this is to:

reduce the amount of calories you eat

increase your levels of activity

This is why experts talk about weight loss in terms of diet and exercise.

Introduce changes gradually

Small changes can make a big difference. One extra biscuit every day adds up to a significant number of calories over a month and then a year. Similarly once the sugar hit of the biscuit goes you are left craving more – one is often never enough.

You're also more likely to stick to, say, swapping full-fat milk for semi-skimmed or making time for a healthy protein and fibre dense breakfast each morning than a diet that sets rules for all foods.

Any changes you make in your weight loss quest should be sustainable. The end game is to sustain these changes over months and years. Simply think of it as a lifestyle not a diet.

Increase your activity levels

Someone who increases the amount they exercise, but maintains the same diet and calorie intake, will almost certainly lose weight.

No matter if you hate gyms – even light exercise, such as a short 20 minute walk, will be beneficial if done most days of the week.

Every single time you exercise more than usual, you burn calories and fat.

There are lots of ways to increase the amount of activity you do. Team sports, racket sports, aerobics classes, running, walking, swimming and cycling will all improve your fitness levels. If you need some motivation or just want to keep an eye on your activity, it could be worth buying a fitness tracker.

Find something you enjoy that's easy for you to do in terms of location and cost. You're then more likely to build it into your routine and continue to exercise, despite inevitably missing the odd session through holidays, family commitments, etc.

Get out and about when you can. Leave your car on the drive and walk to the shops. Try to incorporate longer walks into outings to the park, coast or countryside and take a picnic, so you're in control of what you are going to eat that day.

Every extra step you take helps. Walking up and down stairs uses the larger muscle groups in our legs and is great for burning calories. Always use the stairs instead of the lift, or get off the bus a stop before the usual one and walk the rest of the way.

Use commercial breaks between TV-programmes to stand up and do exercise, or consider using an exercise bicycle in the living room while watching your favourite programme.

Calculate your BMI

Doctors use BMI to assess weight:

A BMI of 18.5 to 25 is healthy

If you have a BMI of more than 25, you're overweight

Over 30 is obese

Over 40 is morbidly obese

To calculate your BMI, you'll need to know your weight in kilos and your height in metres, then follow the example below.

Multiply your height by itself, eg 1.7x1.7= 2.89. Divide your weight (eg 80kg) by this figure. 80 ÷ 2.89= 27.7. Your BMI is 27.7.

If you're overweight, you can't continue with your current eating habits if you really want to lose weight.

Waist to height ratio

Waist to height ratio has been studied in recent years as possibly being even more relevant than BMI to our future health. Measure your waist at the narrowest point in the same units to your height and a value of greater than 0.5 may be an indicator of you being at higher risk for cardiovascular disease and diabetes and so on. This is because this waist measure is more indicative of the visceral fat around our organs than simply measuring our weight or BMI alone. Simply knowing that your clothes do not fit can be a good motivator to losing some weight healthily.

Reduce your calorie intake

It's not possible to reduce body fat while eating lots of food, cakes and sweets. This doesn't mean you can never have any treats, but you need to learn how to limit these foods to small quantities – say, for special occasions.

In terms of weight loss, you can get your body to use up existing stores of fat by eating less and making healthier choices.

This doesn't mean crash diet (a significant calorie drop for you), which usually ends up with you either getting weaker or giving up in desperation. Quick-fix diets can lead to a yo-yoing effect of drastic weight loss followed by weight gain, resulting in a vicious cycle.

There are no shortcuts to losing weight in a healthy and reasonable way.

Eating 300 to 500 calories less per day should lead to a loss of between one and two pounds per week. This is a realistic target. It may seem slow, but it would add up to a weight loss of more than three stone in a year. It might not be so tough to reduce your intake if you are simply consuming a large number of 'empty' non nutritious calories in cakes, sweets, biscuits and fizzy drinks. You just might need to replace these with more healthy choices.

Fat contains the most amount of calories out of all the food types (protein, carbohydrates), so a good way to achieve this is to cut down on fatty foods and eat more wholegrain bread, fruit and vegetables.

Below are ways to reduce calorie intake without having to alter your diet significantly:

Replace fizzy drinks and fruit cordials with water.

Swap whole milk for semi-skimmed, or semi-skimmed for skimmed.

Eat less lunch than usual. For example, make your own sandwich and limit the use of margarine or butter and full-fat mayonnaise (store-bought sandwiches often contain both). Choose healthier breads with wholegrains or make a salad with a good protein source such as chicken, fish or egg.

Stop taking sugar in tea and coffee.

Have smaller portions of the food you enjoy.

Avoid having a second helping at dinner.

Cut out unhealthy treats (such as confectionary, sugary biscuits and crisps) between meals.

Cut down on alcohol intake.

All these things will influence your health in a positive way.

Finally, don't be tempted to skip breakfast – or any meal to lose weight. While skipping a meal will reduce your calorie intake for that hour, it will leave you much hungrier later on.

Not only are you likely to overeat to compensate, but you'll often make bad choices to fill the gap: a cereal bar is not as healthy as a bowl of healthy fortified cereal or as filling, leading you to 'need' something extra for lunch. Wholegrain toast with some avocado will score more healthy points than over-processed sugary cereal in the morning.

Irregular eating habits also disrupt your body's metabolism, which makes it harder to lose weight in the first place.

Keep a food diary

If you're not sure what's wrong with your diet, try keeping a daily diary of everything you eat and drink.

You can use a notebook or an online diary.

At the end of the week, review your entries for problem areas.

Look out for processed foods, alcohol, fast food, roasts, creamy sauces, fried foods.

If your diet seems largely healthy, look at portion sizes.

Once you've decided on what changes you're going to make, write them down.

For example:

Week 1

Exercise: one 20 minute walk every lunch hour.

Alcohol: none in the week, two small glasses of wine on Friday, Saturday, Sunday.

Food: no chocolate or biscuits in the week, choose healthy snacks such as fruit, trim all fat from meat, eat no fried or fast food.

For each week list your targets concerning alcohol, exercise and your food plan. Each day should then be listed in a simple chart and items you have had should be written down. It is also important to make a note of your mood and any comments you would like to get off your chest for each day.

Play the long game

It might take a week or two before you notice any changes, but they will steadily appear. After the first month you'll be able to see the results and measure them in terms of looser fitting clothes.

Keeping your motivation up is one of the most difficult aspects of dieting. There will be days when healthy eating goes out the window, and there will be weeks where you may not lose any weight – or put a little back on.

This is normal for everyone – dieters or not – so don't let it undo your plans for a slimmer you. You're not doing anything 'wrong', but you may need to look at your plan. Do you need to increase your activity levels? Make a few more changes to your diet? Put more effort into sticking to your current plan?

The other side of this is to make sure you celebrate your goals. While there's joy enough in stepping on the scales and seeing them dip lower, be sure to mark long-term progress with a reward – such as new clothes or time off from domestic chores.

Celebrating is also a way to involve your nearest and dearest – it's up to you whether you want their encouragement in the form of gentle reminders not to eat certain foods. But support from other people can get you through the bumpy patches.

Health benefits of weight loss

Studies show that overweight women who lose between 10lb and 20lb halve their risk of developing diabetes. For men, the risk of heart problems reduces considerably.

Generally, we gain weight as we age. A few pounds over the years are not a problem, but people who gain more than 20lb compared to their weight as an 18-year-old will rapidly increase their risk of health problems due to that extra weight. In particular, women increase their risk of heart attack and increase their risk of dying from cancer.

It may seem like these are problems to worry about in the future, but time flies by and tomorrow becomes today. By keeping your weight in the healthy range, you're less likely to be troubled by illnesses in your later years.

Based on a text by Prof Arne Astrup, Dr Carl Brandt

Last updated: 15-04-2020

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