Metabolism and weight loss. How to lose weight without slowing your body down
Your body burns energy every day, even at rest, and to lose weight without slowing that down you need to keep your muscle and avoid eating too little. A slow metabolism rarely explains everything. It does, however, protect itself when you starve it.
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Metabolism, 3 ways you use energy
- At rest. Breathing, keeping your heart beating, holding your body at 37°C. This is the biggest share, around 60 to 70% of daily energy for someone who is not very active.
- Digestion. Digesting and storing food uses around 10% of the energy of the day. Protein takes more to digest than carbohydrate or fat.
- Movement. Exercise, but above all walking, stairs, housework and time on your feet. This is the part that varies most from 1 person to the next.
As a guide, the NHS page on understanding calories says an average man needs about 2,500kcal a day and an average woman about 2,000kcal. Our article on how many calories you need to lose weight goes into more detail.
What changes your metabolism
Size matters, and muscle matters most. A kilo of muscle burns more than a kilo of fat, even while you sleep. 2 people of the same weight do not burn the same amount if 1 of them carries more muscle.
Sleep plays a part too. After short nights, hunger goes up and the urge to move goes down. Poor sleep can also make high-calorie foods more tempting. Stress, finally, pushes you towards richer foods.
Metabolism and age
Age often takes the blame. A large international study published in 2021 in the journal Science found that daily energy use stays stable between 20 and 60, once lean mass is taken into account. It only falls after that, in older people.
What really changes after 40 is muscle, which shrinks if nothing uses it, and a more seated lifestyle. Both can be worked on at any age.
Very strict diets slow your body down
When you eat far less than you need, the body adapts. It loses muscle, burns less and asks for more. That is one of the causes of yo-yo dieting. There is no such thing as a fat-burning food. 3 habits do protect your metabolism, though.
- Protein at every meal, breakfast included. Protein contributes to the maintenance of muscle mass.
- Strength exercises on at least 2 days a week, as the NHS physical activity guidelines recommend.
- A slow pace of loss, without skipping meals. The NHS advises 0.5 to 1kg a week in its weight loss tips.
Our page on muscle and weight loss explains how to keep yours.
At the club
At Witney Nutrition Club, the first assessment is free. Your coach trained in nutrition looks at your daily routine and your meals with you, so that your plan never pushes your body into saving mode.
This article gives general information. It does not replace the advice of your GP or another health professional.
Your weight loss curve
Enter your profile and the curve redraws straight away.
At the median pace, it would take about 11 weeks to lose 8 kg. At the gentlest pace, about 4 months.
The benchmark most often given for lasting weight loss is 500 g to 1 kg a week. That is the ideal zone of the chart. Above 1 kg a week on a regular basis, the body draws on its muscles as much as on its fat. That is the hatched zone.
An indicative projection. Every journey is personal and results vary from person to person. The calculation runs on your device, nothing is saved or sent. Over 65, talk to your doctor first.
How this curve is calculated
The top edge of the zone matches 500 g a week, the gentlest pace. The bottom edge matches 1 kg a week, the risk threshold.
The first weeks go faster, mostly water, then the pace slows. After 40, the median curve slows gradually, because metabolism slows. For the same effort, a man usually loses weight a little faster than a woman.
The journey curve adds plateaus of a few days and small regains, as in real life. It does not predict your own journey.
This advice is general. It does not replace medical advice.
Further reading
For day to day support, see the healthy eating programme.