How to Lose Weight Safely in the UK: A Complete Guide
Weight loss is one of the most common health goals in the UK. According to ONS data, approximately 28% of adults in England are classified as obese, with a further 38% overweight. Understanding the science behind weight loss — and using a reliable calorie deficit calculator — makes it far more achievable.
The Calorie Deficit Principle
Every gram of body fat stores approximately 7.7 kcal of energy. The commonly cited figure of "3,500 calories per pound" (roughly 7,700 kcal per kg) provides a working estimate for fat loss through a calorie deficit. In practice, this means:
- A daily deficit of 500 kcal = approximately 0.5 kg fat loss per week
- A daily deficit of 1,000 kcal = approximately 1 kg fat loss per week
- A daily deficit of 1,500 kcal = approximately 1.5 kg fat loss per week (maximum safe rate)
However, the relationship is not perfectly linear. Early weight loss often includes water and glycogen depletion, which is why the first week or two may show larger drops on the scale than sustained fat loss would produce.
Understanding TDEE and Harris-Benedict
Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns each day. It is calculated in two steps. First, your Basal Metabolic Rate (BMR) — the energy used at complete rest — is estimated using the Harris-Benedict equation:
- Men: BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age)
- Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age)
Your BMR is then multiplied by an activity factor (ranging from 1.2 for sedentary to 1.9 for very physically demanding lifestyles) to give your TDEE. Eating below your TDEE creates the deficit needed for weight loss.
NHS Guidance on Healthy Weight Loss
The NHS recommends losing no more than 0.5 to 1 kg (1 to 2 lbs) per week. This rate is considered medically safe and sustainable. The NHS also advises that women should not consume fewer than 1,200 kcal per day, and men no fewer than 1,500 kcal per day, to avoid nutritional deficiencies.
The NHS Digital Weight Management Programme offers free 12-week online support for adults in England with a BMI over 30 (or over 27.5 for people from some ethnic backgrounds). GP referral is not required for some routes into the programme.
BMI and Healthy Weight Range
Body Mass Index (BMI) is calculated as weight (kg) divided by height in metres squared. The NHS uses the following BMI classifications:
- Under 18.5: Underweight
- 18.5 to 24.9: Healthy weight
- 25.0 to 29.9: Overweight
- 30.0 to 39.9: Obese
- 40 and above: Severely obese
For a person who is 170 cm tall, the NHS healthy weight range is 53.5 kg to 72.0 kg. Our calculator shows your personalised range for your entered height.
Weight Loss Plateaus and Set Point Theory
Most people experience a weight loss plateau after several weeks of consistent dieting. This happens because the body adapts to lower calorie intake through mechanisms including reduced thyroid hormone output, lower spontaneous physical activity and metabolic adaptation. Weighing several kilograms less also means your BMR decreases, since a smaller body requires fewer calories to maintain itself.
Set point theory suggests the body has a preferred weight range it defends through hormonal and neurological signals. The hormones leptin (which signals fullness) and ghrelin (which stimulates hunger) shift in response to weight loss, making sustained calorie restriction increasingly challenging. Strategies to overcome plateaus include refeed days, diet breaks (returning to maintenance calories for 1–2 weeks) and varying exercise types.
Protein and Muscle Preservation During Weight Loss
During a calorie deficit, the body can break down muscle tissue for energy alongside fat. Consuming adequate dietary protein helps preserve lean muscle mass. The general recommendation is 1.6 to 2.2 grams of protein per kilogram of body weight per day for individuals who exercise. For a 70 kg person, this equates to 112 to 154 grams of protein daily. High-protein diets also increase satiety, helping reduce hunger during a deficit.
Good UK protein sources include chicken breast, Greek yoghurt, eggs, cottage cheese, tinned tuna, lentils, chickpeas and quorn. Combining resistance training with a calorie deficit is the most effective approach to preserve muscle while losing fat.
Diet vs Exercise: What Contributes More?
While exercise is essential for overall health, dietary changes typically produce greater calorie deficits with less effort. Running for 30 minutes burns approximately 300 kcal for a 70 kg person — equivalent to a small bar of chocolate. It is considerably easier to not eat 300 kcal than to run 30 minutes to burn it. The most effective approach combines both: a moderate dietary deficit with regular physical activity.
The NHS recommends at least 150 minutes of moderate-intensity aerobic activity per week (such as brisk walking or cycling) alongside muscle-strengthening activities on 2 or more days. This combination supports weight loss, cardiovascular health and mental wellbeing.
Sleep and Weight Loss Hormones
Sleep deprivation significantly impairs weight loss efforts. Studies show that sleeping fewer than 7 hours per night increases ghrelin (hunger hormone) levels by up to 24% and reduces leptin (fullness hormone). Poor sleep also raises cortisol levels, which promotes fat storage — particularly around the abdomen. Aiming for 7 to 9 hours of quality sleep per night supports hormonal balance and makes sticking to a calorie deficit much easier.
Calorie Counting Apps Available in the UK
Several apps can help track calorie intake effectively:
- MyFitnessPal: The most widely used app globally, with a large food database including many UK supermarket own-brand products.
- Nutracheck: UK-specific app with an extensive database of British foods, including Tesco, Sainsbury's, M&S and other supermarket items.
- Cronometer: Excellent for tracking micronutrients alongside calories.
- Lose It!: Simple interface with barcode scanning for packaged foods.
UK Weight Loss Programmes
Several structured programmes are widely used in the UK:
- NHS Digital Weight Management Programme: Free 12-week digital programme for adults in England with a BMI of 30+ (or 27.5+ for some ethnic groups).
- WW (formerly Weight Watchers): Points-based system with weekly group meetings and a digital app. Evidence-based and widely available across the UK.
- Slimming World: Group-based programme using a food optimising approach. Very popular in the UK with thousands of local groups.
- NHS Tier 3 Weight Management: For people with a BMI over 40 (or 35 with comorbidities), offering intensive support including dietitian supervision and psychological support.
Intermittent Fasting and Time-Restricted Eating
Intermittent fasting (IF) approaches such as the 16:8 method (eating within an 8-hour window) or the 5:2 diet (two days of very low calorie intake per week) have become popular in the UK. Research suggests these methods work primarily by reducing overall calorie intake rather than through any unique metabolic mechanism. They can be effective for people who find it easier to skip meals than to count every calorie throughout the day. NHS guidance notes that IF can be safe for most adults but is not recommended for pregnant women, people with a history of eating disorders, or those on certain medications.
Macro Ratios for Weight Loss
While total calorie deficit is the primary driver of weight loss, the proportion of macronutrients (protein, carbohydrates and fat) can influence body composition and hunger. A commonly recommended split for weight loss is approximately 30% protein, 35% carbohydrates and 35% fat. Higher protein intakes support muscle retention and satiety. Lower carbohydrate approaches (such as ketogenic diets) can accelerate initial weight loss through glycogen and water depletion, though long-term outcomes are similar to other approaches when calories are matched.
Calculating Your Healthy Weight Range
The NHS healthy weight range corresponds to a BMI between 18.5 and 24.9. For different heights, the healthy weight ranges are:
- 160 cm: 47.4 kg to 63.7 kg
- 165 cm: 50.4 kg to 67.7 kg
- 170 cm: 53.5 kg to 72.0 kg
- 175 cm: 56.7 kg to 76.3 kg
- 180 cm: 60.0 kg to 80.7 kg
These ranges are guidelines. For older adults, people with high muscle mass, or certain ethnic backgrounds, discuss your individual target with a GP or registered dietitian.
UK Obesity Statistics
According to the NHS Health Survey for England, in 2022 approximately 26% of adults in England were obese (BMI 30+), with a further 38% overweight (BMI 25–29.9). Obesity rates are higher in the North of England and lower in London. Obesity-related conditions including type 2 diabetes, cardiovascular disease and some cancers cost the NHS an estimated £6 billion per year. The UK government's Obesity Strategy includes measures such as restricting advertising of high fat, salt and sugar (HFSS) foods before 9pm and mandatory calorie labelling on menus in large restaurants.
Frequently Asked Questions
How many calories do I need to eat to lose weight?
To lose weight you need to consume fewer calories than your body burns (a calorie deficit). A deficit of 500 kcal per day leads to approximately 0.5 kg of fat loss per week, since roughly 3,500 kcal equals 0.45 kg of fat. Your Total Daily Energy Expenditure (TDEE) — calculated from your basal metabolic rate and activity level — sets your maintenance calories. Eating 500–1,000 kcal below your TDEE is the standard NHS-recommended approach for safe, sustainable weight loss.
How long does it take to lose a stone?
One stone equals 6.35 kg. At a rate of 0.5 kg per week (a 500 kcal daily deficit), losing one stone takes approximately 13 weeks (about 3 months). At 1 kg per week (a 1,000 kcal deficit), it takes around 6–7 weeks. The NHS recommends aiming for 0.5–1 kg per week as a safe and realistic rate. Faster loss is possible early on due to water weight reduction.
Is a 1,000 calorie deficit too much?
A 1,000 kcal daily deficit is at the upper limit of what is considered safe and typically produces around 1 kg of weight loss per week. For most adults this means consuming no fewer than 1,200 kcal (women) or 1,500 kcal (men) per day. Going below these thresholds risks nutrient deficiencies, muscle loss, fatigue and metabolic adaptation. The NHS advises against very low calorie diets (below 800 kcal/day) except under medical supervision.
What is a healthy rate of weight loss?
The NHS and most health authorities recommend losing 0.5–1 kg (1–2 lb) per week as a healthy, sustainable rate. This is achievable through a combined approach of moderate calorie reduction and increased physical activity. Rapid weight loss (more than 1.5 kg per week sustained) increases the risk of gallstones, muscle loss, nutrient deficiencies and rebound weight gain. A slower, steady approach is more likely to result in long-term success.
How does BMI relate to weight loss goals?
BMI (Body Mass Index) is calculated as weight (kg) divided by height (m) squared. The NHS uses BMI to classify weight: under 18.5 is underweight, 18.5–24.9 is healthy, 25–29.9 is overweight, and 30+ is obese. A healthy weight loss goal is typically to achieve a BMI in the healthy range (18.5–24.9). However, BMI does not account for muscle mass, so athletes may show elevated BMI despite being healthy. Waist circumference is also a useful measure alongside BMI.
What does the NHS recommend for weight loss?
The NHS recommends: aiming to lose 0.5–1 kg per week; eating a balanced diet with plenty of fruit, vegetables, wholegrains and lean protein; reducing portion sizes and cutting back on high-calorie processed foods and sugary drinks; increasing physical activity to at least 150 minutes of moderate exercise per week; and seeking support through NHS Weight Management services, including the free NHS Digital Weight Management Programme for adults with obesity or weight-related conditions.