If you're eating less and moving more but the scales won't budge, you're not alone. It's one of the most common frustrations when trying to lose weight, and there's usually more than one reason behind it.
This guide explains why you might not be losing weight, how fast you can realistically expect to lose it, and practical steps that can help.
Quick answer
The most common reasons are:
- eating or drinking more than you realise
- your body needing less energy as you get lighter
- relying on exercise alone
- poor sleep or low mood making it harder to stick to your plan
- a medicine you take, or a health condition that affects your weight
Most of these can be worked through. If you think a medicine or health condition might be involved, speak to a pharmacist or your doctor.
How fast should you expect to lose weight?
After the first few weeks, a healthy rate of weight loss is usually up to about 0.5kg to 1kg (1lb to 2lb) a week. Weight often comes off faster at the start, partly because your body loses water as it uses its stored energy (British Heart Foundation). So if things have slowed down after a good start, that doesn't mean your plan has stopped working.
It also helps to look beyond the scales. NICE encourages people to eat more healthily and be more active even if they don't lose weight, because healthier eating can still improve blood fats and lower the risk of type 2 diabetes and heart disease, and activity has other health benefits too (NICE).
7 common reasons you're not losing weight
1. You're eating more than you think
It's easy to underestimate how much you eat. A Public Health England review found that under-reporting is common whenever people record what they eat, for example forgetting foods and drinks or underestimating portion sizes, and that it's especially common in people living with overweight or obesity (GOV.UK).
Small extras add up quickly: a couple of biscuits with a cup of tea, finishing the children's leftovers, larger portions at the weekend, or oil poured straight from the bottle. None of these matters much on its own, but together they can cancel out the cut you thought you were making.
Try this: for one to two weeks, write down everything you eat and drink as you have it, including snacks, sauces and drinks. Weighing your portions for a few days can be eye-opening.
2. Drinks are adding calories
Sugary drinks are one of the main dietary factors linked with overweight and obesity, and drinking too much alcohol is linked with obesity too (NICE CKS). The British Dietetic Association points out that sugary drinks and alcohol don't fill you up, so their calories come on top of what you eat (BDA).
Check fruit juice, smoothies, sweetened coffees and fizzy drinks, and keep alcohol to no more than 14 units a week, in line with UK guidance (UK Chief Medical Officers; BDA).
3. Your body needs less energy as you get lighter
As you lose weight, your body needs fewer calories to keep going, because there's less of you to maintain (British Heart Foundation). An amount of food that once left you short of what you needed may now be roughly what your body uses, so weight loss slows or stops. This is often called a weight loss plateau.
There's no set definition of how long a plateau lasts. Holidays, life events and festivals can also pause progress for a while. If your weight has stayed the same for several weeks, look again at your portions and activity rather than cutting your food drastically.
4. You're relying on exercise alone
Being active is good for your health whether or not you lose weight. But exercise can also make you hungrier, so it's easy to eat back what you've burned (British Heart Foundation). Losing weight depends on taking in less energy than you use (NICE), so activity works best alongside changes to what you eat, not instead of them.
UK guidance is to build up to at least 150 minutes of moderate activity a week, such as brisk walking, do muscle-strengthening activities on at least 2 days a week, and break up long spells of sitting (GOV.UK).
5. Poor sleep and low mood
Not getting enough sleep is linked with weight gain (NICE CKS). Feeling tired can drive cravings for sugary and fatty foods and make it harder to stick to your plan (British Heart Foundation). Depression and low self-esteem can also lead some people to reach for "comfort foods" (NICE CKS).
A regular bedtime and a wind-down routine can help. If your mood is often low, it's worth talking to your doctor.
6. A medicine you take
Some medicines can cause weight gain. They include steroids, some antidepressants and some medicines for other mental health conditions, insulin and some other diabetes medicines, beta-blockers, and some medicines for epilepsy or nerve pain (NICE CKS).
Don't stop or change a prescribed medicine to lose weight. If you think a medicine is making it harder, ask a pharmacist or your doctor whether there are other options.
7. A health condition or a change in your life stage
Some health conditions can affect weight, including an underactive thyroid, polycystic ovary syndrome (PCOS), Cushing's syndrome and conditions that cause fluid to build up in the body. Perimenopause and menopause are also linked with weight gain (NICE CKS).
If you've put on weight without changing what you eat or how active you are, or you have other new symptoms, speak to your doctor.
In a calorie deficit but not losing weight?
A calorie deficit means taking in less energy than your body uses (NICE). If you're sure you're in one but the scales aren't moving, the deficit may be smaller than you think. Online calculators can only estimate how much energy you need, portions can creep up without you noticing, and your needs fall as you lose weight (see reasons 1 and 3).
If you're already eating very little, cutting back further on your own isn't the answer. NICE advises that diets of 800 to 1,200 calories a day should only be used as part of a specialist weight management programme with long-term support (NICE), and that restrictive diets that aren't nutritionally balanced don't work in the long term and can be harmful (NICE CKS).
What you can do now
- Track honestly. Write down what you eat and drink for one to two weeks.
- Weigh less often. Weigh yourself about once a week, at the same time of day, and look at the trend over several weeks rather than a single reading.
- Measure your waist as well as your weight. NICE uses waist-to-height ratio alongside BMI to estimate fat around the middle (NICE CKS), so a smaller waist can show progress the scales miss.
- Check your drinks. Swap sugary drinks for water and keep alcohol within UK guidance.
- Plan your meals. Cooking at home makes portions easier to judge. For balanced ideas, try our one-pan chicken and roasted veg traybake or lemon chicken traybake with crispy potatoes.
- Keep moving. Build activity into your week, including strength exercises on 2 days.
- Look after your sleep.
Progress is rarely a straight line, so try not to judge your efforts by one week.
When to get support
If you've been making changes for a while without results, or your weight is affecting your health, talking it through with someone can help. Our pharmacist-led weight-loss consultation starts with a few health questions online. You can then speak with one of our pharmacists about your options, including whether treatment is right for you.
If you have questions first, you can contact our team.
Sources
- NICE Clinical Knowledge Summaries: obesity, causes and risk factors, last revised June 2026
- NICE Clinical Knowledge Summaries: obesity, management, last revised June 2026
- NICE guideline NG246: overweight and obesity management, physical activity and diet
- GOV.UK: UK Chief Medical Officers' physical activity guidelines, updated 10 July 2026
- GOV.UK: Calorie reduction, the scope and ambition for action, Public Health England, March 2018
- GOV.UK: UK Chief Medical Officers' low risk drinking guidelines, August 2016
- British Heart Foundation: Weight loss plateau and Why am I not losing weight?, both by a BHF dietitian, May 2024
- British Dietetic Association: Weight loss food fact sheet, September 2026
Frequently asked questions
How long does a weight loss plateau last?+
There's no set definition of how long a plateau lasts. Holidays, life events and festivals can also pause progress for a while. If your weight has stayed the same for several weeks, look again at your portions and activity rather than cutting your food drastically.
Can you be in a calorie deficit and not lose weight?+
If you're sure you're in one but the scales aren't moving, the deficit may be smaller than you think. Online calculators can only estimate how much energy you need, portions can creep up without you noticing, and your needs fall as you lose weight.
How fast should I expect to lose weight?+
After the first few weeks, a healthy rate of weight loss is usually up to about 0.5kg to 1kg (1lb to 2lb) a week. Weight often comes off faster at the start, partly because your body loses water as it uses its stored energy.
Can a medicine make it harder to lose weight?+
Some medicines can cause weight gain. Don't stop or change a prescribed medicine to lose weight. If you think a medicine is making it harder, ask a pharmacist or your doctor whether there are other options.
