How quickly should you lose weight?

Reviewed by our clinical team

It’s estimated that around two-thirds of adults in the UK are either overweight or obese. So, it’s no surprise that losing weight and different methods of losing weight are such popular topics. But sometimes it can be hard to filter out the noise of fad diets and ‘miracle’ superfoods which claim to help you ‘lose weight fast’ and work out which is the right method for you.

In fact, losing weight very quickly isn’t usually the best way to do it, and it can mean you’re more likely to put the weight back on and potentially experience side effects. In this article we’re going to look at how quickly you should lose weight and what might happen if it’s too fast.

How quickly should you lose weight? 

If you’re trying to lose weight, it’s best to do it slowly. Generally, the advice is to try and lose around 0.5-1kg a week (1lb to 2lbs). This would usually mean trying to burn between 500 and 1000 calories more than you consume. To lose weight at the right pace, the NHS recommends women reduce their daily calorie intake to 1400 and men to 1900 (these are both 500 calories under the usual recommended daily allowance). And you should also be aiming for at least 150 minutes of moderate activity each week. Moderate activity is really anything that gets your heart rate up a bit, making you breathe faster and feel warmer.

Can you lose weight too quickly? 

The short answer is yes, you can lose weight too quickly. Crash or fad diets are often about losing weight rapidly and they can work. But often losing weight quickly isn’t good for you in the long run, Crash diets can make it harder for you to lose weight in the future because of the ways crash dieting affects how your body works.

Weight loss should be all about making long-term changes to your diet and lifestyle which are sustainable. Crash diets can’t be kept up and you can often end up putting weight back on and for some people it will lead to weight gain in the long run.  

Side effects of losing weight too quickly 

Losing weight too quickly can have a big impact on the way your body works and your general health. 

Slower metabolism 

Losing weight really quickly can impact how efficiently your body burns calories when it’s resting (e.g., when you’re sat at your desk working, watching TV or sleeping) – this is known as your resting metabolic rate (RMR).  

Losing weight rapidly often means drastically restricting and reducing your calorie intake. Because your body isn’t getting the energy it had before, it wants to preserve energy resources, meaning you’ll burn fewer calories when you’re not active.

Effectively, crash dieting can slow your metabolism down, making it harder to lose weight and much easier to put weight back on when you’re not dieting. 

Metabolic diseases 

Slowing down your metabolism can lead to an increased risk of metabolic conditions like heart disease, type 2 diabetes and strokes.  

You lose muscle mass 

Rapid weight loss will make you lose muscle mass as well as fat. This can make it harder in the future to lose weight because muscles burn a lot of calories, but with less muscle you’ll be burning less. That’s why you should try and exercise alongside reducing calories, so you can preserve muscle mass while losing weight. 

Visceral fat accumulation 

There is some evidence that people who yo-yo diet (alternate between intense crash diets and returning to their old habits) have more fat around their internal organs. This is called visceral fat accumulation. This kind of fat can lead to an increased risk of heart disease and diabetes. 

Nutrient deficiencies 

Restrictive diets that can aid rapid weight loss can often mean cutting out certain food groups. This can mean you’re not getting all the nutrients your need to keep you healthy. 

Cravings

Dramatically cutting calories can make your body very low on energy, this can lead to craving high-sugar, high-fat foods. If you can’t manage these cravings this could lead to putting any weight lost back on again.

Hair loss 

Some people who lose weight extremely rapidly will find they also experience hair loss. 

Other reasons for rapid weight loss 

If you’re not on a crash diet and notice that you’re losing weight unintentionally you should speak to your GP about it. There are lots of reasons people lose weight unintentionally, these include: 

• Digestive conditions like irritable bowel syndrome, coeliac disease, ulcerative colitis and Crohn’s  
• Overactive thyroid 
• Type 2 diabetes 
• Heart failure 
• Certain cancers 
• Depression, anxiety and stress 
• Obsessive compulsive disorder (OCD) 
• Eating disorders

You GP will try and help you work out why you might be losing weight and they might send you for more tests or refer you to a specialist.

How to lose weight at the right pace 

As we’ve mentioned, the best way to lose weight and keep it off is gradually. It’s all about reducing your calorie intake and increasing the amount of exercise you get. Aim to lose no more than 1kg a week and try to burn 500 more calories than you’re eating. Ideally you don’t want to cut out any food groups, but eat a balanced diet, rich in nutrients and vitamins. 

The NHS has a lot of resources on the best way to lose weight, you might find their 12-week plan a helpful place to start.  

Support on your weight loss journey 

At Online Doctor, we’re here to help you on your weight loss journey. We have a whole library of weight loss and lifestyle advice articles, filled with tips and support from our clinicians.

We also have a number of treatments such as Mounjaro®, Wegovy®, Orlistat and Xenical which can help you on your weight loss journey. When combined with a reduced calorie diet and increased activity, weight loss treatments can give your body the extra support it needs to lose weight. Read our guide to medicated weight loss here.  

References 

https://www.gov.uk/government/news/new-obesity-strategy-unveiled-as-country-urged-to-lose-weight-to-beat-coronavirus-covid-19-and-protect-the-nhs
https://assets.nhs.uk/tools/download-panels/data/weight-loss/pdf/all-weeks.pdf
https://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/weight-loss/art-20047752 
https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/ten-weight-loss-myths/ 
https://patient.info/news-and-features/why-fad-diets-can-actually-lead-to-weight-gain  
https://patient.info/news-and-features/how-can-crash-diets-affect-your-metabolic-flexibility 
https://www.nhs.uk/conditions/unintentional-weight-loss/