Why can't I lose weight despite diet and exercise?

If your weight is not going down despite diet and exercise, first check whether you really are eating less than you use. Many people eat more and move less than they think. Weight loss is also made harder by some medicines, too little sleep and untreated conditions such as an underactive thyroid (hypothyroidism). Obesity is a chronic disease. After you lose weight, your appetite increases and your body uses less energy, so losing more becomes harder. According to the 2024 guidelines of the Polish Society for the Treatment of Obesity (PTLO), people with obesity who change only their habits usually lose no more than 3-5% of their body weight. If they have not lost 5% after 3-6 months, the doctor should talk to them about obesity medication (1).

In brief

• In a small 1992 study, people with obesity who were not losing weight despite dieting had a normal metabolism, but they under-reported the calories they ate by an average of 47%. A food diary and weighing your portions help you spot where the calories don't add up.
• Some medicines can make weight loss harder: antidepressants, antipsychotics, diabetes medicines and steroids. Short studies suggest that too little sleep also gets in the way. If a medicine is causing weight gain, do not stop it on your own.
• After weight loss, appetite increases. In a study of people with type 2 diabetes, researchers calculated that participants ate about 100 kcal a day more for every kilogram they lost. This is one reason why people with obesity who change only their habits usually lose no more than 3-5% of their body weight.
• If your BMI is at least 30 (or at least 27 with a weight-related condition) and 3-6 months of habit changes have not brought a 5% weight loss, the doctor should talk to you about obesity medication. Bring your diary, your weigh-in results, a list of your medicines and specific questions to the appointment.

How do you know your weight has really stalled?

To say that your weight has stalled, you need measurements taken over several weeks under the same conditions, as well as a waist measurement. Your weight varies from day to day because the amount of water in your body and the contents of your bowels change. That is why doctors recommend weighing yourself once a week, in the morning, on the same scales and in similar conditions.

The optimal rate of weight loss is about 1 kg in the first week and then about 0.5 kg a week, which comes to roughly 2 kg a month. To lose weight at this rate, you need to eat 500-600 kcal a day less than your body needs (1). Later, weight loss slows down because the body adapts to getting less food. A lighter body also needs less energy, so the same meal plan may stop creating a deficit. That is why you need to recalculate your calorie needs once you have lost 10% of your body weight.

Once a month, measure your waist halfway between the lower edge of your ribs and the top of your hip bone. Scales show fat, muscle, bone and water all together, while waist circumference gives an indirect indication of how much fat surrounds the organs in your abdomen. If your weight has stalled but your waist is getting smaller, this usually means the changes to your eating and activity are working.

If you are already taking an obesity medicine, the doctor also looks at the dose and how long you have been treated, and checks whether you are taking it as prescribed. We cover this in our article on what to do when your weight stalls on obesity medication.

Could you be eating more than you think?

Yes. A review of 59 studies involving 6,298 adults compared how much participants said they ate with measurements of the energy they actually used. In most of the studies, people reported fewer calories than they really ate (2). You do not have to hide anything to get this wrong: it is hard to remember every spoonful of oil and every snack, and portions judged by eye are easy to get wrong.

In 1992, American researchers studied ten people with obesity who had been unable to lose weight for a long time, although they said they ate fewer than 1,200 kcal a day. For two weeks, the researchers measured exactly how much they ate and how much energy they used. Their metabolism was normal. However, they under-reported the calories they ate by an average of 47% and over-reported their physical activity by 51% (3). Ten people is a small group, so this study cannot tell us how often such errors happen. It does show how large they can be.

How can you check how much you really eat and move?

For two weeks, including weekends, keep a diary following a few rules:

• Write everything down straight after eating, not in the evening from memory
• Weigh your portions on kitchen scales, including oil, butter, sauces, nuts and bread
• Record all drinks: juices, sweetened drinks, coffee with milk or syrup, and alcohol
• Note meals out, parties and food at work as carefully as meals at home
• Record physical activity in minutes and steps
• Weigh yourself once a week in the morning, on the same scales

A diary like this shows the doctor and dietitian how you are following the recommendations and what you find difficult. If your diary shows a deficit but your weight and waist have not changed for several weeks, take it with you to your doctor's appointment.

What else besides food can make weight loss harder?

Start by looking at the medicines you take and your sleep. At the appointment, you will discuss your medicines, any shift or night work, your mental wellbeing and any eating disorders. If your symptoms point to a hormonal disease, the doctor will order tests. Untreated depression can also contribute to weight gain.

Which medicines make it harder to lose weight?

Some antipsychotics, antidepressants, diabetes medicines and corticosteroids (steroids) can contribute to weight gain. Before starting an obesity medicine, the doctor should consider stopping them or switching to a different medicine (1). However, do not stop such a medicine on your own, because the condition it was prescribed for may come back. The decision about an alternative is made by the doctor treating that condition. In our article on weight gain caused by medicines, we explain which substances promote weight gain and how obesity is treated when a medicine cannot be stopped or changed.

Does lack of sleep make it harder to lose weight?

Two studies suggest that it does. In the first, a small one, ten adults who were overweight followed the same diet for two weeks on two separate occasions. On one occasion they were allowed 8.5 hours in bed, on the other only 5.5 hours. With shorter sleep, they lost 0.6 kg of fat instead of 1.4 kg, but more fat-free mass, which is mainly muscle and water. They were also hungrier (4). The second study included 80 people aged 21-40 who were overweight and usually slept less than 6.5 hours. They were randomly divided into two groups. People in the first group received individual advice on how to sleep longer. They slept an average of 1.2 hours longer and, over two weeks, ate about 270 kcal a day less than the other group, even though no one had told them to diet (5). Both studies were short and involved people who were overweight, not people with obesity. It is therefore not known whether the effect lasts over the following months or whether it also applies to people with obesity.

Can thyroid problems, insulin resistance or PCOS stop you losing weight?

TSH is tested in everyone with obesity, because untreated overt hypothyroidism makes effective obesity treatment impossible (1). Once hypothyroidism is controlled with medication, however, body weight changes very little: in a study of 101 adults with newly diagnosed hypothyroidism, the typical weight loss was 0.1 kg (6). The doctor does not routinely order insulin or HOMA-IR tests for everyone with obesity. Polycystic ovary syndrome (PCOS) is checked for in women with irregular periods.

Do stress and cortisol block weight loss?

Only about 0.9% of people with obesity have excess cortisol (hypercortisolaemia). The doctor does not routinely test everyone for Cushing's syndrome. A test is ordered when there are symptoms: bruising easily, wide, bright red stretch marks, weakness in the thigh and upper arm muscles, or abdominal obesity together with type 2 diabetes, high blood pressure or osteoporosis. The first test is then the 1 mg dexamethasone suppression test, not a morning blood cortisol measurement (1).

Chronic stress can encourage emotional eating. When food is your main way of dealing with stress, working with a psychologist helps. In our article on binge eating and emotional eating, we explain when this kind of eating becomes a disorder.

Is it harder to lose weight after quitting smoking or if you drink alcohol?

Your weight may go up after you quit smoking. For your health, however, this is far less dangerous than continuing to smoke. We have collected ways to limit this weight gain in our article on weight gain after quitting smoking. Alcohol also provides calories, and it is easy to leave out of a food diary. In our article on how giving up alcohol affects body weight, we describe how much weight you can lose after stopping drinking and how to stop safely.

Why does your body defend its weight after a diet?

After weight loss, appetite increases, energy expenditure falls, and the hormones that regulate hunger and fullness take a long time to return to their pre-diet levels. This is a biological mechanism that works regardless of effort and motivation.

In a one-year study, 153 people with type 2 diabetes lost weight on a diabetes medicine that makes the body pass some glucose, and with it some calories, in the urine. Using a mathematical model, researchers calculated that participants ate about 100 kcal a day more than at the start for every kilogram they lost, because their appetite increased. This increase was more than three times larger than the fall in energy expenditure (7). In another study, 50 people lost an average of 13.5 kg in 10 weeks on a very low-calorie diet. A year later, their levels of leptin, ghrelin and other hormones that regulate hunger and fullness were still different from their pre-diet values, and the participants were hungrier (8). In our article on the yo-yo effect after dieting, we describe how this mechanism encourages weight regain. Obesity medicines act on appetite regulation. Doctors use them when changing habits alone is not enough.

When should you see a doctor if your diet isn't working?

If your BMI is at least 30, or your waist measures at least 80 cm (women) or 94 cm (men), you need to see a doctor. These results indicate obesity or abdominal obesity. The doctor discusses obesity medication with you if your body weight has not fallen by 5% after 3-6 months of habit changes (1).

If your situation matches one of the last three rows of the table, you can start with a GP (family doctor) or with the obesity treatment programme at Nasz Gabinet, which lasts six months and takes place online. The programme includes video consultations with a doctor and with a psychologist. The doctor diagnoses the condition based on your BMI and waist circumference, assesses your blood test results and decides, according to the Polish guidelines, whether medication is indicated. If it is, the doctor issues an e-prescription after each medical review. You buy the medicine at a pharmacy, because its cost is not included in the programme. Every month, the doctor assesses your progress using data from the app, where you enter your weight once a week and your body measurements once a month. If your drinking is hazardous, we also refer you to our addiction treatment clinic alongside the programme. In our article on eligibility for obesity medication, we explain who a doctor will prescribe medication for and why they may refuse.

Which symptoms alongside weight gain need prompt medical attention?

• If your weight is rising quickly and your feet, ankles or legs are swelling, or you get short of breath during everyday activities or when lying down, contact a doctor the same day. These can be symptoms of heart failure. If you are severely short of breath, find it hard to breathe or speak, or your lips or skin turn blue or grey, you need immediate medical help (9).
• If you bruise easily, have wide, bright red stretch marks and your thigh and upper-arm muscles are getting weaker, don't put off seeing a doctor. The doctor will assess whether you need to be tested for excess cortisol.
• Loud snoring with pauses in breathing and sleepiness during the day can be symptoms of sleep apnoea. It is diagnosed with a sleep study, which your doctor refers you for.
• If you gain a noticeable amount of weight after starting a new medicine, tell the doctor who prescribed it. Do not stop the treatment on your own.

What should you say if your doctor brushes off your weight problem?

It is best to come with your diary and measurements and to ask specific questions. According to the Polish guidelines, the doctor should look for the causes of obesity and value the patient's efforts, not only their results. The doctor should also not make it harder for a patient to access treatment because of their weight. The authors of the guidelines point out that obesity is not just a matter of discipline but also of disrupted energy regulation in the body.

Take these with you to the appointment:

• A food and activity diary from the last two weeks
• Your weekly weigh-in results and waist measurements from recent months
• A list of all your medicines with doses, including those prescribed by other doctors
• Your weight history: your lowest and highest weight as an adult and the circumstances in which you gained weight
• A description of previous attempts to lose weight: when, what method, what result and what happened afterwards
• Information about your sleep, shift work, mood and episodes of binge eating
• Blood test results from recent months, if you have them

In our article on tests before obesity treatment, we explain which tests a GP orders and what each of them shows.

It is best to describe the facts and finish with a question. You can use sentences like these and fill in your own details:

• I have been keeping a diary for three months and weighing myself once a week, and my weight has gone down by less than 5%.
• Based on my BMI and waist measurement, would you diagnose obesity?
• Could any of my medicines be making it harder to lose weight, and is there an alternative?
• Which tests should I have to check my thyroid and any complications of obesity?
• According to the guidelines of the Polish Society for the Treatment of Obesity, is obesity medication indicated for me? If not, what do we do next?

If the doctor still ends the conversation by telling you simply to eat less, you can go to a different GP or book a private appointment, with no referral needed, with a doctor who treats obesity. In our guide on where to start obesity treatment, we explain who to see and how to prepare for your first appointment.

Frequently asked questions

Can you be in a calorie deficit and still not lose weight?

For a week or two, yes. Over such a short time, the reading on the scales also depends on water and the contents of your bowels, so fat loss may not show. That is why results are compared over several weeks and waist measurement is checked too. If your weight and waist stay the same for longer even though your diary shows a deficit, some of what you eat may not be making it into the diary. If you have already lost weight, your calorie needs may also have fallen, and then they need to be recalculated. Medicines or too little sleep can also make weight loss harder.

What does it mean if your weight stays the same but your waist gets smaller?

It is usually a good sign. Waist circumference gives an indirect indication of the amount of fat around the organs in your abdomen, whereas scales also show muscle, bone and water. Keep measuring under the same conditions and compare your results over several weeks.

Which doctor should you see if you can't lose weight?

Start with your GP. The GP should be the first to measure your weight and height, diagnose overweight or obesity and discuss further treatment with you. You can also book a private appointment, with no referral needed, with a doctor who treats obesity. The doctor refers you to an endocrinologist when your results or symptoms suggest a hormonal disease.

Will a doctor prescribe obesity medication if dieting isn't working?

A doctor may prescribe medication if your BMI is at least 30, or 27-29.9 with a weight-related condition, and your weight has not fallen by 5% after 3-6 months of habit changes. Before writing a prescription, the doctor checks for contraindications and reviews your test results. Ozempic, which patients often ask about, is a medicine for type 2 diabetes (10). Medicines that are not licensed for treating obesity should not be used for it.

Sources

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2. Burrows TL, Ho YY, Rollo ME, Collins CE. Validity of Dietary Assessment Methods When Compared to the Method of Doubly Labeled Water: A Systematic Review in Adults. Front Endocrinol (Lausanne). 2019;10:850. PMID 31920966, DOI
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4. Nedeltcheva AV, Kilkus JM, Imperial J et al. Insufficient sleep undermines dietary efforts to reduce adiposity. Ann Intern Med. 2010;153(7):435-441. PMID 20921542, DOI
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6. Lee SY, Braverman LE, Pearce EN. Changes in body weight after treatment of primary hypothyroidism with levothyroxine. Endocr Pract. 2014;20(11):1122-1128. PMID 24936556, DOI
7. Polidori D, Sanghvi A, Seeley RJ, Hall KD. How Strongly Does Appetite Counter Weight Loss? Quantification of the Feedback Control of Human Energy Intake. Obesity (Silver Spring). 2016;24(11):2289-2295. PMID 27804272, DOI
8. Sumithran P, Prendergast LA, Delbridge E et al. Long-term persistence of hormonal adaptations to weight loss. N Engl J Med. 2011;365(17):1597-1604. PMID 22029981, DOI
9. NHS. Heart failure - symptoms. nhs.uk
10. Charakterystyka Produktu Leczniczego Ozempic (semaglutyd), roztwór do wstrzykiwań, punkt 4.1 (Polish summary of product characteristics). Europejska Agencja Leków (European Medicines Agency). ema.europa.eu