To Lose Weight: How Many Calories Should I Eat?

To lose weight, how many calories you should consume depends on several personal factors, but most UK adults are advised to reduce their daily intake by around 500 to 600 kcal to achieve a safe, gradual loss of roughly 0.5 kg per week. Rather than following a single universal figure, your ideal calorie target should reflect your age, sex, body composition, activity level and any relevant health conditions. This article explains how to estimate a safe calorie deficit, which foods support satiety, and when to seek professional guidance from your GP or a registered dietitian.

How many calories should I eat a day to lose weight?

Most UK adults are advised to reduce daily intake by around 500 to 600 kcal, with the NHS suggesting roughly 1,400 kcal for women and 1,900 kcal for men as illustrative starting points. Very low energy diets of 800 kcal or fewer require medical supervision.

Most adults in the UK are advised to reduce their daily calorie intake by around 500 to 600 kcal to achieve a gradual, sustainable rate of weight loss of roughly 0.5 kg per week. This range reflects the general approach described in NICE obesity management guidance, though the precise deficit that is right for any individual will vary. As a broad, illustrative starting point, the NHS Weight Loss Plan suggests a daily intake of around 1,400 kcal for women and around 1,900 kcal for men who are aiming to lose weight, but these are examples rather than universal prescriptions, and your own target should be based on your personal circumstances.

The right number for any individual depends on a range of personal factors, which means a figure that works well for one person may be too low or too high for another.

It is worth noting that very low energy diets, typically defined as 800 kcal per day or fewer, should only be followed under medical supervision.^[1][8] Dropping calories too sharply can lead to nutrient deficiencies, muscle loss and fatigue, and is unlikely to be sustainable in the long term. A moderate, consistent reduction is generally more effective and safer than a dramatic short-term cut.

For those considering structured weight management support, a range of options exists, from NHS referral pathways to regulated online services. Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, where clinically appropriate options may be discussed. Whichever route you choose, working with a qualified professional helps ensure your calorie target is tailored to your health needs rather than based on a generic number.

What affects how many calories your body actually needs?

Calorie needs are determined by basal metabolic rate combined with activity level, and are influenced by age, sex, muscle mass, height, health conditions and certain medications. Two people of the same weight can have meaningfully different daily calorie requirements.

The number of calories your body needs each day is determined primarily by your basal metabolic rate (BMR), which is the energy required to keep your body functioning at rest, combined with the additional calories burned through physical activity and daily movement. BMR is influenced by several individual characteristics, meaning two people of the same weight can have meaningfully different calorie requirements.

Key factors that affect your calorie needs include:

• Age: Metabolic rate tends to decline gradually with age, so older adults generally need fewer calories than younger adults of the same size.^[9]

• Sex: Men typically have a higher proportion of muscle mass, which burns more energy at rest, so they often have higher calorie requirements than women of similar weight.

• Body composition: Muscle tissue is more metabolically active than fat tissue, so people with greater muscle mass burn more calories even when sedentary.^[10]

• Height and current weight: Larger bodies require more energy to maintain basic functions.

• Activity level: Someone with a physically demanding job or who exercises regularly will need considerably more calories than a sedentary person of the same size.

• Health conditions: Certain conditions, including thyroid disorders, polycystic ovary syndrome (PCOS) and type 2 diabetes, can affect metabolism and make weight management more complex.^[6][11] If you think a health condition may be affecting your weight, speak to your GP.

• Medications: Some medicines, including certain antidepressants, corticosteroids and antipsychotics, can influence appetite and weight.^[6] Do not stop or change any prescribed medicine because of weight concerns without first speaking to your GP or pharmacist.

Understanding these variables is important because it explains why calorie calculators and population averages are only a starting point. A personalised assessment, ideally with a GP, dietitian or qualified clinician, gives a far more accurate picture of your individual needs.

How do you work out a safe calorie target for weight loss?

Calculate your total daily energy expenditure (TDEE) using a validated calculator, then apply a deficit of around 500 to 600 kcal in line with NICE guidance. Reassess your target periodically as your weight changes and calorie needs shift.

A safe calorie target for weight loss can be estimated by first calculating your total daily energy expenditure (TDEE) and then applying a modest deficit, in line with NICE guidance of around 500 to 600 kcal per day, to achieve a gradual loss of roughly 0.5 kg per week. TDEE is calculated by multiplying your BMR by an activity factor that reflects how physically active you are across the week.

Several validated equations are used to estimate BMR, and many reputable online calculators incorporate these. The NHS website also provides general guidance on healthy weight and calorie awareness. However, these tools produce estimates, not exact figures, and should be treated as a starting point.

A practical approach to setting a calorie target involves:

1. Estimating your TDEE using a reliable calculator based on your age, sex, height, weight and activity level.
2. Applying a moderate deficit of around 500 to 600 kcal from that figure, in line with NICE obesity management guidance.
3. Ensuring nutritional adequacy: NICE guidance distinguishes between low-energy diets (around 800 to 1,600 kcal per day) and very low energy diets (800 kcal per day or fewer). Very low energy diets require medical supervision. For most people, staying within the low-energy diet range and prioritising nutritional quality is the safer approach.
4. Monitoring progress regularly: Weight loss is rarely perfectly linear. Reassess your target periodically as your body weight changes, since your calorie needs will shift as you lose weight.
5. Prioritising nutrient quality: Hitting a calorie target with nutritionally poor foods is less effective than meeting it with a balanced diet rich in protein, fibre, vitamins and minerals.

If you have a complex medical history or have struggled to lose weight despite reducing calories, a referral to a dietitian through your GP is the most appropriate next step.

Which foods help you feel full on fewer calories?

High-protein foods and high-fibre foods are most effective at promoting satiety, helping you consume fewer calories without feeling hungry. Foods with high water content, such as soups and salads, also add meal volume without significantly increasing calorie intake.

Foods that are high in protein and dietary fibre are the most effective at promoting satiety, meaning they help you feel full for longer while consuming fewer overall calories. This is a well-established principle in nutrition science and forms the basis of many evidence-informed dietary approaches to weight management.

High-protein foods increase levels of satiety hormones and reduce hunger signals.^[12] Good sources include:

• Lean meats such as chicken breast and turkey

• Fish and seafood, including oily fish like salmon and mackerel

• Eggs

• Low-fat dairy products such as Greek yoghurt and cottage cheese

• Legumes including lentils, chickpeas and kidney beans

• Tofu and tempeh for plant-based diets

High-fibre foods slow digestion and help stabilise blood sugar levels, reducing the likelihood of energy dips and cravings.^[4][5] Good sources include:

• Vegetables, particularly leafy greens, broccoli, carrots and courgettes

• Whole grains such as oats, wholemeal bread and brown rice

• Fruit, especially berries, apples and pears

• Pulses and legumes (which also provide protein)

Foods with high water content, such as soups, salads, cucumbers and watermelon, add volume to meals without adding many calories, which can help manage portion sizes naturally.

Conversely, foods high in fat, salt and sugar, as well as sugary drinks, tend to be calorie-dense but low in satiety, making it easier to overconsume them without feeling satisfied. The NHS Eatwell Guide recommends limiting these foods and drinks and building meals around starchy wholegrains, vegetables, fruit, protein and dairy or dairy alternatives.^[5] Eating slowly and mindfully also supports satiety, as it takes time for fullness cues to develop after a meal.

When should you talk to your GP about losing weight?

See your GP if dietary changes and exercise have not produced results after several months, your BMI is 30 kg/m² or above, or a health condition may be affecting your weight. Your GP can investigate underlying causes and refer you to appropriate weight management services.

You should talk to your GP about losing weight if dietary changes and increased physical activity have not produced results after several months, or if your weight is affecting your physical or mental health. Your GP can assess whether an underlying medical condition, such as hypothyroidism or insulin resistance, may be contributing to difficulty losing weight, and can refer you to appropriate services including dietetic support or structured weight management programmes.

There are specific circumstances where seeking GP advice promptly is particularly important:

• Your BMI is 30 kg/m² or above, or 27.5 kg/m² or above if you are from a South Asian, Chinese, Black African or Black Caribbean background, as NICE guidance uses lower BMI thresholds for these groups when assessing weight-related health risk.^[7][8] You can check your BMI using the NHS BMI healthy weight calculator.

• You have a weight-related health condition such as type 2 diabetes, high blood pressure, sleep apnoea or joint problems that are being worsened by excess weight.

• You are considering a very low energy diet (800 kcal per day or fewer), which requires medical supervision.

• You have a history of disordered eating, as calorie restriction without appropriate specialist support can be harmful in this context. Your GP can refer you to NHS eating disorder services.

• You are pregnant, as weight-loss dieting is not appropriate during pregnancy and nutritional needs are increased. Speak to your midwife or GP for guidance on healthy eating in pregnancy.

• You are breastfeeding and wish to lose weight, as crash diets and very restrictive eating are not recommended. NHS guidance advises ensuring adequate nutrition while breastfeeding; if you wish to lose weight during this period, seek advice from your GP or a dietitian to do so safely and gradually.

• You are experiencing unexplained or rapid weight loss without trying, which warrants investigation regardless of your weight management goals.

Your GP can also discuss whether you meet the criteria for NHS-commissioned weight management interventions, including referral to specialist services. Access to these services is determined locally and may depend on criteria set by your Integrated Care Board (ICB) as well as NICE eligibility thresholds. If you need advice outside of GP hours, NHS 111 can direct you to the appropriate service. Weight management is a clinical matter, and professional guidance ensures that any approach you take is safe and suited to your individual circumstances.

Scientific References

1. Overweight and obesity management – Physical activity and diet (NG246).
2. Calories and weight loss – Better Health.
3. How to lose weight – Better Health.
4. Healthy eating when trying to lose weight – Better Health.
5. The Eatwell Guide.
6. Overweight and obesity in adults.
7. Overweight and obesity management – Identifying and assessing overweight, obesity and central adiposity (NG246).
8. Overweight and obesity management (NG246) – full guideline PDF.
9. Is there evidence for an age-related reduction in metabolic rate? Piers LS et al. J Appl Physiol. 1998..
10. Skeletal muscle metabolism is a major determinant of resting energy expenditure. Zurlo F et al. J Clin Invest. 1990..
11. An update in the management of polycystic ovary syndrome. Orio F et al. Minerva Endocrinol. 2016..
12. The effects of high protein diets on thermogenesis, satiety and weight loss. Halton TL, Hu FB. J Am Coll Nutr. 2004..
13. Very low energy diets in the treatment of obesity. Mustajoki P, Pekkarinen T. Obes Rev. 2001..
14. Breastfeeding and diet.
15. Keeping fit and healthy with a baby.

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