How to lower your BMI

BMI and weight loss: how to lower your body mass index

You've calculated your score, but now comes the real work of bringing it down. For decades, the advice on lowering your BMI has followed two seemingly straightforward rules: eat less, move more. Simple. Tidy. But, for a lot of people, it's slightly more complicated.

The truth is, lowering your BMI is a biological process shaped by hormones, genetics, sleep, stress, and the small daily habits that quietly add up over months and years.¹ Understanding how your BMI changes, and what you can do to support it, is the first step towards lasting results.

So, what does it actually take to lower your BMI in a way your body can sustain? And how do you know when your body needs a little extra help to stay in a healthy range?

What does it mean to lower your BMI?

Lowering your BMI means reducing your total body mass - specifically fat mass - relative to your height. The number shifts when the composition shifts.

But the number isn't the whole story. Moving from one risk category into another - obese to overweight, overweight to a healthy range - is where the real gains live. Each shift brings measurable improvements in metabolic health, cardiovascular function, and long-term wellbeing.²

Why a slow pace matters

It's tempting to try to lose weight as quickly as possible, but the quicker you lose weight, the more likely you are to lose things your body needs to hold onto.

A healthy rate of weight loss sits between 0.5kg and 1kg per week, in line with the NHS "Better Health" and NICE guidance.³,⁴ If you drop weight faster than that, your body starts to burn lean muscle, and your bone density starts to deplete.² Keeping these intact is crucial for maintaining a strong metabolism, steady movement, strong bones, and health resilience into later life.⁵

Going slow supports achievable and sustainable long-term outcomes.

The three pillars of BMI reduction

Sustainable BMI reduction rests on three pillars: what you eat, how you move, and how you recover. Neglect any of them, and your progress will stall.

What you eat

Weight loss begins with a calorie deficit - burning more energy than you take in. In theory, simple. In practice, it's a balancing act.

Cut too much, too quickly, and your body fights back. Hunger spikes,⁶ energy drops, fatigue sets in,⁷ and muscle disappears along with the fat as the body seeks alternative fuel sources.² Cut too little, and the number on the scales doesn't budge.

When it comes to calories, protein should do most of the heavy lifting. Aim for 1.2 to 1.6 grams per kilogram of body weight each day.⁸ It protects the lean muscle you want to keep while your body taps fat stores for fuel,⁹ and keeps you fuller for longer. This will make holding the deficit feel less like a battle.

How you move

Most evidence-based approaches combine two forms of training, working together:

• Aerobic exercise - walking, cycling, swimming - burns calories and strengthens your heart.

• Resistance training - weights or bodyweight - keeps your muscle maintained and your metabolism ticking over.

Muscle is metabolically active tissue.¹ The more you keep, the more energy your body burns at rest. In short: cardio drives the calorie deficit, and lifting keeps your muscles working.

How you recover

This is the pillar that gets overlooked most often, and the one with the highest payoff.

A poor night's sleep raises hunger hormones and leaves you reaching for quick energy fixes the next day.⁷ Chronic stress pushes cortisol up,¹⁰ which encourages fat to settle around your abdomen.¹¹ Even mild dehydration dulls appetite signals, energy, and focus.¹²

And crash diets? They fail for a reason. Extreme restriction of any kind strips lean muscle, slows your metabolism, and amplifies cravings. The evidence consistently shows that gradual, structured change outperforms severe restriction across every measure that matters.⁶

Key facts: reducing your BMI safely

1. To lower your BMI, you must consistently burn more energy than you consume.⁴

2. Losing 5-10% of your body weight can significantly reduce your BMI and improve heart health.⁷

3. A healthy BMI range for most UK adults is 18.5 to 24.9.¹³

4. Resistance training helps lower BMI by maintaining muscle mass while losing body fat.¹⁴

5. A sustainable pace of weight loss is 0.5kg-1kg per week.³

When lifestyle changes aren't enough

The diet industry has spent decades telling a simple story: if the weight isn't coming off, you aren't trying hard enough. It's a story designed to make you feel like you're not doing it right. And for a lot of people, it simply isn't true.¹⁵

Body weight is regulated by a complex network of hormones and genes. Leptin, ghrelin, and insulin each decide when you're hungry, when you're full, and how readily your body stores what it takes in.^16,17,9 In some people, these systems push harder than lifestyle changes can counter. The body defends a higher "set point" weight,² and sustained loss becomes genuinely, biologically difficult.

Busting the myths about medical weight loss

Medical weight loss has come a long way, but the myths around it are taking their time to catch up. Let's clear a few up:

"It's a shortcut for people who can't be bothered." False. Eligibility is assessed by clinicians, and treatment sits alongside nutritional guidance and coaching, not in place of them.

"GLP-1 medications are a quick fix." Sustained results come with sustained effort. Medication supports a calorie deficit by regulating appetite and fullness.¹² The work is still yours.

"If I stop the medication, I'll regain everything." Habits built during treatment - balanced eating, movement, sleep - are what carry the results forward. Stopping without them is what drives weight regain, not the medication itself.

How weight loss treatment can help you lower your BMI

This is where GLP-1 receptor agonists come in. Originally developed for type 2 diabetes, they now play a significant role in medical weight management. They work by mimicking a natural hormone that regulates appetite and fullness.¹¹

Patients often describe the same shift: quieter hunger, earlier satiety, and fewer cravings. A calorie deficit that used to feel exhausting starts to feel manageable.

At Numan, GLP-1 medications are prescribed only by UK-registered clinicians, following a thorough medical review. Weight loss medications are a tool which works best alongside nutritional guidance, activity plans, lifestyle advice, and one-to-one coaching.

Is a weight management treatment programme right for you?

Treatment is generally considered for patients with a BMI of 30 or above, or a BMI of 27 or above with a weight-related health condition such as Type 2 diabetes, high blood pressure, or obstructive sleep apnoea. Your clinician will assess whether it's right for you during your consultation.

Realistic timelines and tracking your progress

Sustainable weight loss is a long game. The scale rarely moves in a straight line, and it can be easy to feel discouraged if you're focused on the numbers alone.

What does progress look like?

In clinical trials, weight loss typically follows a predictable curve. During the first 4 weeks, weight loss is often modest (0–2kg) as the body adapts to new habits or medication titration.¹¹ By month 3 (12 weeks), patients often achieve a clinically significant 5% reduction in total body weight.⁹ By month 12 (approximately 72 weeks in trials), structured programmes using GLP-1 medications can deliver sustained losses of around 20% of initial body weight - 20.7% with semaglutide 7.2mg¹⁸, comparable to over 20% with tirzepatide.⁶

Look beyond the scale

BMI is an important health marker, but it only tells part of the story.

Waist circumference is a sharper predictor of metabolic risk, and worth tracking monthly. So is your energy, your sleep, how your clothes fit, and how easily you get up from the floor. These signals often shift long before the scale catches up.

When progress slows

Weight loss slows as your body gets smaller. Fewer calories burned at rest means the deficit you started with eventually stops having the same impact.

When this happens, your health coach can help you reassess your intake, adjust your training, and learn how to be patient with the pace. Plateaus aren't the end of progress. They're a signal to adapt what you're already doing to give you the best chance of success.

Take control with Numan

The Numan Weight Loss Programme brings clinician-prescribed medication, tailored meal plans, and one-to-one coaching into one place. Every journey is medically supervised by UK-registered clinicians, with regular check-ins to review progress and adjust your plan as you go.

We don't promise a number on the scale. We offer evidence-based support, delivered by people who understand both the science and the person taking the step.

The numan take

Managing your BMI is about creating a long-term partnership with your body. By combining consistent daily habits with evidence-based medical support, you can create a sustainable environment where your body can find its healthy balance.

References

1. Speakman JR, et al. Set points, settling points and some alternative models: Theoretical options to understand how genes and environments combine to regulate body adiposity. Dis Model Mech. 2011;4(6):733-45.

2. Cava E, et al. Preserving Healthy Muscle during Weight Loss. Adv Nutr. 2017;8(3):511-519.

3. Sardeli AV, et al. Resistance Training Prevents Muscle Loss Induced by Caloric Restriction in Obese Elderly Individuals: A Systematic Review and Meta-Analysis. Nutrients. 2018;10(4):423.

4. Hall KD, Kahan S. Maintenance of Lost Weight and Long-Term Management of Obesity. Med Clin North Am. 2018;102(1):183-197.

5. Neeland IJ, et al. Visceral and ectopic fat, atherosclerosis, and cardiometabolic disease: a position statement. Lancet Diabetes Endocrinol. 2019;7(9):715–725.

6. Jastreboff AM, et al. (SURMOUNT-1 Study Group). Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387:205-217.

7. National Institute for Health and Care Excellence (NICE). Overweight and obesity management [NG246]. London: NICE; 2023.

8. Caleyachetty R, et al. Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study. Lancet Diabetes Endocrinol. 2021;9(7):419–426.

9. Wilding JPH, et al. (STEP 1 Study Group). Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384:989-1002.

10. NICE. Semaglutide for managing overweight and obesity [TA875]. London: NICE; 2023.

11. NHS England. Better Health: Lose Weight [Internet]. 2024. Available from: https://www.nhs.uk/better-health/lose-weight/

12. Wu Y, et al. Advantages and limitations of the body mass index (BMI) to assess adult obesity. Int J Environ Res Public Health. 2024;21(6):757.

13. Sweatt K, et al. Strengths and limitations of BMI in the diagnosis of obesity: what is the path forward? Curr Obes Rep. 2024;13(3):584–595.

14. Rahman MS, et al. Role of insulin in health and disease: An update. Int J Mol Sci. 2021;22(12):6403.

15. Alam MK, et al. Exploring hormonal dynamics in obesity: Leptin, ghrelin, and nesfatin-1. Med-Science. 2024;13(1):210-6.

16. NICE. Tirzepatide for managing overweight and obesity [TA1026]. London: NICE; 2024.

17. Milano W, et al. Depression and obesity: Analysis of common biomarkers. Diseases. 2020;8(2):23.

18. Wharton S, et al. Once-weekly semaglutide 7·2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial. Lancet Diabetes Endocrinol. 2025.