How to lose weight: why losing weight alone isn't enough

Most people who come to me wanting to lose weight have already tried something. Sometimes several things, sometimes more than once. And usually it worked for a while, until the weight stopped, or until it came back after a few months, sometimes with a bit extra.

That isn't a question of willpower. It's a question of how the weight loss was approached.

Where it starts: energy balance

There's no way around it. For fat to go down, your body has to use more energy than it takes in. No food, supplement or exercise changes that.

At the same time, it's the least useful information anyone can give you. Because the question is not whether to be in a deficit, but how to create one you can live with, and without losing what you don't want to lose.

And this is where the paths split.

What you lose when you lose weight

Muscle lost when dieting, enlarge

When your body gets less energy than it needs, it reaches into its reserves. But it doesn't only reach into fat.

You lose both fat and muscle mass. The ratio depends on training and protein intake. When you lose weight without strength training, roughly a quarter of the loss can be fat-free mass, mainly muscle and water. With enough protein, and above all with regular load, that share can be cut down considerably.

Why it matters:

Muscle burns energy even at rest. Not dramatically, a kilo of muscle burns about 13 calories a day at rest. When you lose a few kilos of it, your resting expenditure drops by a few dozen calories, and next time you'll need less food than before to keep the same weight. That's one of the reasons weight comes back after diets.

Muscle holds your shape. Two people with the same weight and height can look completely different depending on how much of that weight is muscle and how much is fat. Most people who want to “lose weight” actually want to look different, and that's a question of body composition, not the number on the scales.

Muscle is function. Getting up from a chair, carrying shopping, managing stairs, catching yourself when you trip. All of this weakens with age, and losing weight without strength training speeds up that decline.

Why strength training, and not just cardio

The common idea is that cardio is for losing weight and weights are for muscle. In reality it works differently.

Cardio burns more calories per hour. That's true. An hour of brisk walking or running has a higher immediate expenditure than an hour in the gym, where half the time goes on rests between sets.

What takes your muscle while you lose weight is the deficit. Strength training, however, protects it far better than cardio. In a study of older adults, the strength group lost 2% of their fat-free mass, compared with 5% in the cardio group.

Strength training is a signal. When a muscle gets regular load, your body judges it as necessary and spares it while you lose weight. Its main role in weight loss lies not in how many calories you burn doing it, but in what you keep.

Both is ideal. But if you had to choose one, strength training affects the result more than you would expect.

The reality: how much training actually burns

What a week adds up to, enlarge

This is where the biggest disappointment usually is, so I'll say it straight.

An hour in the gym burns roughly 250 to 350 calories, and up to four or five hundred for a heavier person at high intensity. With three sessions a week, that is around 900 calories a week.

A kilo of fat corresponds to roughly 7,700 calories.

So three sessions a week on their own mean something in the order of 100 grams of fat a week, and not even all of that, because your body would have burned part of that energy sitting down anyway. It isn't negligible, but it's far from what people expect from the gym.

That doesn't mean training is pointless. Its job is to make sure the weight loss goes in the right direction and that the result lasts.

Where the result is really made

Food decides more than training

You affect much more through food than through training. One sweet coffee and a croissant can have up to 500 calories, more than a whole training session. It isn't fair, but that's how it is.

A specific meal plan, however, isn't a trainer's job. It belongs to a nutrition adviser or a dietitian, who takes into account your health, tastes, possibilities and schedule. I can point you in a general direction, not put together a plan.

What can be said in general:

Protein is key when you're losing weight. It protects muscle, keeps you full better than other nutrients, and digesting it costs energy in itself. In my experience, most clients who are losing weight eat less of it than they should.

Too big a deficit doesn't pay off. Losing weight fast takes more muscle, and in one study the people who lost more muscle went on to regain more weight. In my experience the main reason for a moderate pace is simpler, though: it fits into normal life. A sensible pace is roughly half a kilo a week, for some people even less.

Only a plan you stick to counts. A plan you stick to for three weeks loses to a plan you stick to for a year, even if the second one looks worse on paper.

The biggest reserve is outside the gym

This is where most of the unused room is hidden, especially if you have a desk job.

Walking, stairs, moving around the office, a walk after lunch, all of this together burns more calories than the training itself, because it happens every day and adds up to hours.

Ten thousand steps isn't a magic number, but the difference between three and eight thousand steps a day burns more over a week than three extra training sessions.

Why the number on the scales is misleading

Same weight, different body, enlarge

This is where a lot of people fail.

In the first few weeks, the number on the scales often doesn't change, or even goes up. The reasons:

• Muscle that has started responding to training holds more water
• Glycogen stores in the muscles fill up and bind water
• Your gut reacts to the change in diet
• Hormonal fluctuations: over the course of a menstrual cycle, around half a kilo of water, for some people even more, shows up on the scales without anything changing in your body composition

And yet underneath all of that, you may be losing fat.

That's why I recommend measuring body composition at the start, for example with InBody. Not for the number itself, but so there's something to measure progress against. When a second measurement after six weeks shows the same weight, but muscle mass has gone up and fat has gone down, that's good news. Without the measurement, the same thing would look like failure.

Apart from weight, it's worth tracking:

• Measurements (waist, hips, thigh): in my experience they often move before the weight does
• Photos: once a month, in the same light and position
• The load on the bar: when it goes up at the same body weight, exactly what should be happening is happening
• How your clothes fit

What it should look like in practice

Strength training two to three times a week. Whole body, basic movements: squat, hip hinge, push, pull. Not twenty exercises, but five to seven done properly.

Cardio as an addition, not the foundation. Intervals once a week, plus as much walking as possible.

Protein in every meal.

Cut your intake a little, not dramatically.

Patience for three months. Not much happens in three weeks. A lot happens in three months, if you stick with it.

What if you have already tried something

Most people who come back after a failed attempt didn't go wrong in their choice of exercises, or by eating carbs in the evening. They ran into one of two things:

Strictness. Intake cut so far that you couldn't live with it, and a plan that couldn't be kept up alongside work and family. It lasted six weeks and then collapsed.

Or they left strength training out. They lost weight, but muscle went along with the fat, and keeping the lower weight was harder than they expected.

Both can be fixed. But not by repeating the same thing with more determination. How to set up a fresh start so that it lasts this time is in my article Getting back to the gym after a break.

When to see a doctor

Before you set out to lose a larger amount of weight, it's worth having a preventive check-up, especially if:

• you're over 40 and haven't been active for a long time
• you have high blood pressure, diabetes or heart problems
• you take medication regularly
• your weight fluctuates without you changing anything
• you have felt tired for a long time without an obvious reason

That last one is worth paying attention to. Tiredness and weight gain without a change in diet can have a cause that training won't fix (the thyroid, for example).

Summary

Losing weight comes down to building something you can keep up, and keeping the muscle that holds your shape, function and metabolism.

Strength training tells your body to keep its muscle, food creates the deficit and daily movement deepens it more than anyone would expect. Time takes care of the rest, and time can't be sped up.

If you take away only one thing: don't measure success by weight alone and don't expect a result in three weeks. Most often it doesn't work out for people because they stopped before the result had time to show.

If you have a specific health restriction or take medication, talk to your doctor before changing your routine. Putting together a meal plan belongs to a nutrition adviser. This article describes general principles, not individual recommendations.

Sources: Heymsfield et al. (2014), Obesity Reviews. Wang et al. (2010), American Journal of Clinical Nutrition. Villareal et al. (2017), New England Journal of Medicine. Schumann et al. (2022), Sports Medicine. Vink et al. (2016), Obesity. Purcell et al. (2014), Lancet Diabetes & Endocrinology. Wycherley et al. (2012), American Journal of Clinical Nutrition. Hall et al. (2011), The Lancet. Herrmann et al. (2024), Journal of Sport and Health Science. Levine et al. (2005), Science. Kanellakis et al. (2023), American Journal of Human Biology. World Health Organization, guidelines on physical activity (2020).