Fat loss: what the science actually says and why the gym decides your result

Google the term fat loss and you'll get three answers: the fat-burning heart rate, ab exercises, and a tub of capsules. In light of the research, all three are either beside the point or flat-out misleading.

Real fat loss comes down to an energy deficit: fat comes off when you burn more energy than you take in from food. But how much of what you lose is actually fat isn't settled by diet alone — it's settled by how you train. Strength training is what matters here, because it determines whether the weight that leaves your body is mostly fat or muscle mass as well.

If your goal is to lose fat and you want to do it right without guessing, this piece is for you. We'll go through the science behind fat loss, why the energy deficit matters, what strength training does, the common myths such as the role of the fat-burning heart rate and spot reduction, and what a training program that actually supports fat loss looks like in practice.

Once you understand these fundamentals, you'll avoid the most common mistakes and improve your body composition more effectively than with diets that drop weight but take the wrong tissue with them — muscle instead of fat. So let's go through what the research says and bury a few stubborn myths along the way.

Before you read on: this piece explains how fat loss works when that's your goal. It isn't a statement that it should be.

A low body-fat percentage isn't a measure of health. The health benefits come mainly from training regularly, eating enough protein, and sleeping well — regardless of what the scale shows. If you're a healthy weight and feel good, strength training without an energy deficit is usually a better goal than dieting.

And if you notice that thinking about food or your body is taking up an outsized amount of space, causing anxiety, or having a negative effect on your daily life, health, or relationships, an energy deficit isn't the thing to try next. In that case it's worth talking to a doctor, a dietitian, or another professional. In Finland, the eating-disorder association SYLI ry offers free guidance services.

Fat loss in brief

• Fat loss requires an energy deficit. A sensible pace is 0.5–1% of body weight per week.

• Strength training decides how much of the weight you lose is fat. Without strength training, roughly 20% of weight loss comes from fat-free mass.

• Protein: 1.8–2.2 g per kilogram of body weight per day.

• The fat-burning heart rate sits at around 60–70% of your maximum, but it's not relevant to the bigger picture. Fat loss is decided by total energy expenditure.

• Spot reduction doesn't work. In a meta-analysis of 13 studies and 1,158 participants, the effect size was −0.03.

• When fat loss stalls, the reason is almost always your energy intake or a drop in everyday activity — not your metabolism.

How does fat loss actually work?

First, let's get the terms straight, because they get mixed up constantly. Losing weight means the number on the scale goes down, whether the mass that left was fat, muscle, or water. Fat loss specifically means a reduction in fat tissue. The distinction matters, because it's what decides how the result looks. In fat loss your weight can even hold steady while your body changes noticeably.

Fat tissue is the body's energy store. It shrinks when, over a stretch of time, you burn more energy than you take in from food. This isn't a matter of opinion. It's thermodynamics, and it holds whether you create the deficit by eating less, moving more, or both. Your body also uses fat for energy at rest, to keep its basic functions running, so your metabolism is part of this picture too.

In practice the exact arithmetic rarely lands on the mark as a diet progresses. The further a diet goes, the more tightly your body clings to its fat stores. As you diet longer, resting energy expenditure drops, the production of thyroid and satiety hormones shifts, and spontaneous everyday movement quietly decreases. The media often calls this phenomenon "metabolic adaptation" or "starvation mode," and total energy expenditure can fall by more than 10% beyond what you'd expect. A meaningful slowdown in energy expenditure does, admittedly, only set in once fat mass is already clearly low (in other words, the lower your body-fat percentage, the harder fat is to shift).

How bad can it get? There are two extreme examples. In the classic Minnesota Starvation Experiment, the subjects' basal metabolic rate fell from roughly 1,609 kilocalories to 981 kilocalories per day, and the calculated adaptation in total expenditure was about 1,488 kcal/day. In The Biggest Loser study, the corresponding adaptation after 30 weeks was on the order of 1,750 kcal/day. These, however, are extreme cases from extreme conditions. The same body of research also shows that even in these cases weight kept coming off when energy intake was low enough.

So metabolic adaptation is a real phenomenon. But it isn't the reason your diet isn't progressing. Usually the reason is far more boring: your energy intake is higher than you imagine, or the deficit is so severe you can only stick to it two weeks at a time. We'll go through the most common reasons in more detail below.

For most people a sensible rate of loss is 0.5–1% of body weight per week. The lower end suits leaner, more trained individuals; the upper end applies when there's plenty of excess weight to lose. A faster pace is possible, but you pay for it in muscle mass, in your energy for everyday life and training, and in how long you can keep the diet going.

What does this mean in calories? One kilogram of fat tissue corresponds to roughly 7,000 kilocalories, so a half-kilo-per-week pace requires an average deficit of about 500 kcal per day. A workable starting point for most people is 15–25% of estimated total expenditure. Avoid the 1,000 kcal deficits that circulate online: they produce a fast start followed by muscle loss, collapsing gym performance, and a rebound.

Which burns fat better, weight training or aerobic exercise?

This is where many people expect an argument that strength training burns a huge number of calories. That would be a poor argument. An hour at the gym burns roughly the same as a brisk walk, and the so-called afterburn effect — EPOC — amounts to tens of kilocalories, not hundreds. The claims of 40- or 48-hour afterburn that circulate online rest on individual small studies with exceptionally brutal training protocols, and the magnitude is typically a few dozen kilocalories. A kilogram of muscle burns an estimated 12–14 kcal per day at rest. That's roughly half a mandarin. Muscle mass does raise resting metabolism, but so little that it explains nothing on its own.

The gym's importance for fat loss lies elsewhere. The energy deficit decides how much mass leaves your body. Strength training decides how much of it is fat.

Without strength training, roughly 20% of weight loss on average comes from fat-free mass, and toward the end of a diet the share is often larger. Kraemer's group's classic work showed that properly done strength training preserves muscle on a diet better than endurance training alone. Murphy and Koehler's 2022 meta-analysis refined the picture in an interesting way: an energy deficit impairs the gain in fat-free mass from strength training, but not the development of strength. A deficit of around 500 kcal/day was enough to wipe out the muscle gain that would have been achieved in energy balance. Strength, however, still went up.

Let's turn this into a practical example. If you lose ten kilos on diet and walks alone, two of those kilos might be muscle. If you also train strength properly, you can keep practically all of it. In the first case the scale shows a faster result. In the second, the mirror shows a better one.

And here's the whole point: people don't actually want to "lose weight." They want to look good and feel good. That result comes from what's left behind once the fat is gone.

What about the fat-burning heart rate everyone talks about most? The short answer is that the 60–70% heart-rate zone physiologically exists and is still a poor training instruction. We'll come back to that in more detail below.

How much protein do you need for fat loss?

When energy is scarce, your body takes the amino acids it needs from somewhere. Adequate protein intake makes muscle a less appealing target.

In Longland's group's study, 2.4 g/kg of protein preserved muscle clearly better than 1.2 g/kg, and in beginners muscle mass even increased despite the energy deficit. Pasiakos's group found that both 1.6 g/kg and 2.4 g/kg beat 0.8 g/kg, with no meaningful difference between the two higher amounts. The practical recommendation lands at 1.8–2.4 g/kg per day for most people. The upper end is justified when the deficit is severe and body fat is already low. If you're aiming for muscle growth, a lower level is enough, and we cover that in more detail in our article on how much protein per day. Protein alone isn't enough, though — your diet also needs enough total energy, because your body needs fuel for recovery and for holding onto muscle mass. If you eat too little, progress can stall even when you're aiming for fat loss, because of how the body adapts.

Split your intake across at least three meals — in practice about 3–5 meals a day works well. Eat regularly, because spreading protein over several meals helps support muscle during an energy deficit. It's usually not worth cutting carbohydrates entirely, since you need them for training and recovery. More than 2.2 g/kg brings no added benefit for muscle mass, so overdoing it is pointless. What protein does do is keep you full, which on a diet is a more valuable trait in practice than any talk of mechanisms.

What kind of training program supports fat loss?

Here are the variables that actually matter:

Train every muscle group at least twice a week. A muscle group trained once a week gets less stimulus to hold onto muscle mass, and on a diet you need more stimulus, not less.

Keep weekly volume in the 5–20 set range per muscle group. For a beginner the lower end is plenty. For the more experienced, during a deficit it's often best to stay around the middle, because recovery capacity is reduced.

Hold onto progressive overload. This is the single most important instruction on a diet. When the bar weighs the same or more than it did a month ago, your muscles are still getting the mechanical stimulus they need. The reassuring message of Murphy and Koehler's meta-analysis was exactly that: strength develops even in an energy deficit. If your set weights start sliding downward week after week, the deficit is too severe or recovery is failing.

Take your sets close enough to failure. In an energy deficit it's tempting to leave sets too light, because training starts to feel harder and your body looks for ways to conserve energy. For stimulus, though, a set taken to within 1–3 reps of failure is the one that tells the muscle it's still needed. Energy expenditure from training also stays closer to before when your sets remain just as challenging.

Use cardio as a supplement. Two or three lighter endurance sessions a week add to energy expenditure, support recovery, and improve fitness. In practice it's worth doing aerobic exercise 2–3 times a week at a light or moderate intensity, so it supports recovery rather than eating into the quality of your gym training. HIIT can be a useful addition if it doesn't compromise the quality of your gym training or your recovery. If cardio starts to eat into the quality of your gym work, there's too much of it.

Sleep. Sleep is surprisingly important for effective fat loss and a well-functioning metabolism, because even a few bad nights can impair hormone function and recovery. Recovery is a prerequisite for the training and daily choices that support effective fat loss. Too little sleep raises the stress hormone cortisol, and poor sleep can distort hunger and increase cravings. It's still worth understanding how the effect works: cortisol doesn't block the use of fat for energy, nor does it make an energy deficit ineffective. Sleep deprivation raises the hunger hormone ghrelin and lowers the satiety hormone leptin, so you eat more, and when you're tired your gym training gets lighter and your daily step count falls. Chronic stress impairs recovery and makes fat loss harder precisely through energy balance and behavior. The end result shows up in energy balance, not as some mysterious "fat lock." That's why, for the sake of fat loss, it's worth building routines that support recovery too and aiming for 7–9 hours of sleep a night.

These principles are enough to evaluate a program. If you want a ready-made example of what they look like in practice, work through our three-day sample program with exercises and set counts.

Use coaching that accounts for your diet and recovery. The problem with most programs downloaded off the internet is that they were written once and know nothing about your situation. They don't know that you're in your third month of dieting and your recovery capacity is different from what it was in January. Use individualized coaching. AITOFIT, for example, builds a program based on your starting level, your goals, and the time you have available, and adjusts volume and load according to how your training actually goes. When the energy deficit starts to bite, the program has to account for your recovery and how loaded your body is, not just training volume.

Why won't fat loss get started?

This is by far the most common question on the topic, and there are a handful of recurring answers. Here they are in order of frequency, not order of interest.

1. Your energy intake is higher than you think

This is so often the reason that it's worth checking before you consider anything else. In food-diary studies, people systematically underestimate how much they eat, typically by 20–40%. It isn't lying. It's that the oil in the frying pan, the bite grabbed off a child's plate, and the two weekend beers don't make it into the log. Weigh your food for a week before you decide the problem is your metabolism.

2. Your everyday activity has quietly collapsed

When your energy intake drops, your body conserves energy in ways you don't notice. Your step count falls. You take the elevator instead of the stairs. Moving becomes more economical — the same work gets done with less energy. This spontaneous everyday activity is called NEAT in the research literature, and it's the most variable part of total energy expenditure. Often, when people say a diet has slowed the metabolism, what's really happening is that this general everyday energy expenditure has decreased.

The same phenomenon explains much of why added exercise rarely produces as much weight loss as the calculator promises. When you train an extra hard hour a day, your body compensates by moving less otherwise and often by eating more. This is called exercise energy compensation, and it's well documented.

Even so, effective fat loss doesn't require tricks around your daily expenditure. Track your step count, for example, and keep it roughly constant throughout the diet. It's one of the few metrics that flag metabolic adaptation in real time. Tracking your training volume matters too.

3. You're measuring the wrong thing

The number on the scale swings 1–3 kilos a day depending on fluid balance, salt intake, the menstrual cycle, and the contents of your digestive tract. If you weigh yourself once a week and compare individual readings, you're essentially measuring noise. Weigh yourself on three or four mornings a week and track weekly averages over two- or three-week windows. Only then do you see the trend.

4. The deficit is too severe to sustain

This one is the most insidious, because it looks like the opposite problem. When the deficit is too big, the diet progresses for two weeks, then a weekend eats the entire gain, and the next Monday starts from scratch. By the end of the month the average deficit is zero, even though the weekdays were miserable. A moderate deficit you can sustain for six months beats a severe one you can manage two weeks at a time.

5. The diet has run too long without a break

Energy expenditure falls as a diet progresses, partly because you're moving a lighter body and partly because of adaptation. At some point the original deficit has shrunk to zero even though you're still eating the same amount. At that point you have two options: tighten by 10%, or spend a couple of weeks at maintenance and then continue. Both work. Grinding away in place does not.

What's the best heart rate for fat loss?

You often hear that there's a specific fat-burning heart rate you have to train at a lot in order to burn fat. Behind this myth is a genuine physiological observation: as exercise intensity rises, the share of fat as fuel falls and the share of carbohydrate rises. So in low-intensity exercise a larger percentage of energy comes from fat.

Concretely, the fat-burning heart rate refers to about 60–70% of your maximum, and fat oxidation typically peaks in that range. The figure is correct. The problem is what people conclude from it. Light walking might draw 60–70% of its energy from fat, a hard interval maybe 10–30%, but the total expenditure of an interval session is many times greater. So the percentage is an interesting physiological detail and a poor training instruction. Use heart-rate zones for what they're meant for — building fitness and managing load.

The ratio of carbohydrate to fat as fuel during exercise therefore tells you nothing about changes in body composition. Total energy expenditure, once again, is behind everything. And more importantly: what you burn during a workout doesn't decide what happens to your fat stores over weeks and months. What's decisive is cumulative energy balance — whether, as the weeks go by, you've been in a clear energy deficit or not.

Steele and colleagues' meta-analysis compared interval training, including HIIT, with steady-state endurance training for changes in body composition. The difference in fat mass was essentially zero, a pooled effect size of −0.02 (95% confidence interval −0.07 to 0.04), and the certainty of the evidence was high by GRADE criteria. In fat-free mass the difference was smaller still.

The more interesting finding, though, was how modest the results of both training modes were. Interval training reduced fat mass by an average of 0.20 kg and steady-state by 0.25 kg. So cardio on its own is a fairly weak fat-loss tool. It's excellent for health, fitness, and holding weight gain in check, and it's also a useful way to add to energy expenditure and support fat loss — but on the evidence it isn't superior to steady-state endurance training. It isn't the engine of fat loss, even though exercise can of course burn fat; over 80% of the fat you burn ultimately leaves the body as carbon dioxide, through your breath.

The same goes for fasted training. In a twelve-week study, strength training done fasted and fed produced the same changes in body composition, muscle thickness, strength, and power. Fat loss doesn't speed up because you skip breakfast. Do it if it feels better.

Can you burn belly fat with ab exercises?

Can ab exercises burn belly fat? No, ab exercises don't burn belly fat. This has been studied thoroughly, and the result is unambiguous.

A systematic review and meta-analysis pooled 13 high-quality studies and 1,158 participants. They compared changes in fat tissue in a trained limb versus an untrained one. The pooled effect size was −0.03 (95% confidence interval −0.10 to 0.05). Of 37 comparisons, 17 favored the trained limb and 20 the untrained one. In other words, the result was a coin flip.

Fat is mobilized systemically, and where it comes off the body first is largely dictated by genetics and hormonal profile. You can influence how much fat comes off. The order in which it leaves, you can't.

The practical conclusion is reassuring: you can stop doing sets of 300 crunches and spend that same time on exercises that load your big muscle groups. They burn more energy, build more muscle, and produce the muscle tissue that ultimately shows once the fat layer thins.

Should you train with light weights and long sets on a diet?

This is perhaps the most stubborn gym myth of all. The idea is that on a diet you should switch to lighter weights and longer sets, because that "tones" and burns more fat. The rationale given is that lighter weights mean more mechanical work per set, so the energy expenditure from the workout is greater.

Carlson's group tested this in a randomized crossover study published in 2022. It involved 130 trained individuals who completed a four-week heavy block (about 80% of 1RM, under 10 reps per set) and a four-week light block (about 60% of 1RM, under 20 reps per set) in an energy deficit.

The results were practically identical. Fat mass fell by 0.67 kg in the heavy block and 0.55 kg in the light one. Fat-free mass rose by 0.06 kg in the heavy block and 0.22 kg in the light one. The differences were negligible, and nowhere near statistical significance. Strength levels developed the same way.

If the greater energy expenditure of lighter training were a meaningful factor in fat loss, it should have shown up here. It didn't.

So choose your rep range according to your goal, and in a way that lets you do quality sets taken close enough to failure without your technique breaking down. For most people that means somewhere between 5 and 15 reps, with the emphasis depending on the exercise. The word "toning" can be laid to rest.

Do fat burners work?

The promise of fat-burner supplements is simple: speed up your metabolism, blunt your hunger, and fat practically "melts" away. The evidence is more modest.

Siedler's group studied the effects of a commercial thermogenic fat burner over four weeks in 52 training individuals. A statistically significant difference in resting energy expenditure was found versus the control group, about 111 kcal/day. Sounds good. But no difference at all was found in body composition, appetite, sleep quality, energy intake, or physical activity. Clark and Welch's 2021 meta-analysis reached the same conclusion: fat burners don't produce a meaningful benefit for weight loss.

Caffeine is a good lesson here. In one randomized trial, a 1 mg/kg dose of caffeine reduced energy eaten at breakfast by about 10%. There was no difference in energy intake over the whole day. The blunting of appetite was temporary and was compensated for at later meals. L-carnitine, meanwhile, has gradually shifted in marketing from a fat-loss supplement to a recovery supplement, which tells its own story — that supplements are marketed according to whatever happens to be trendy at the time.

And then there's the quality question: when researchers analyzed plant-based supplements promising fat loss and performance, the amount of active ingredient was within 10% of what the label claimed in only 11% of them. 12% of the products contained at least one FDA-banned substance. Not one of the turkesterone products tested contained even 1% of the promised dose.

Caffeine — also marketed as having fat-loss-enhancing effects — can of course be useful in other ways. It reduces fatigue and improves gym performance, and that matters when energy is low. As a fat burner it still isn't worth buying, and it is, fortunately, among the safe substances.

Three pieces of advice worth ignoring

"Snacking blocks fat loss, eat every 3–5 hours"

The rationale given is insulin: every meal raises insulin, insulin slows the release of fat from fat cells, so eating frequently should keep the body constantly out of fat-burning mode. The mechanism is acutely correct. The conclusion isn't. Over the course of a day, fat storage and release alternate continuously, and the net balance is determined by energy balance. When calories and protein are held constant, meal frequency doesn't affect fat loss.

Meal timing does matter, for two other reasons. Splitting protein across 3–5 meals a day supports the retention of muscle mass, and a regular rhythm helps most people stay full. So choose your number of meals by what keeps you full and lets you spread your protein, not by what supposedly unlocks fat loss. A rhythm like that helps support muscle on a diet.

"Cut the carbs, keto boosts fat loss"

When protein and total energy are held constant, low-carb and high-carb diets produce practically the same fat loss. At the start of ketosis the scale drops quickly because water leaves along with your glycogen stores, which is why the approach feels more effective than it is. For someone who trains at the gym, cutting carbs drastically is also directly harmful, because the quality of your sets and your strength levels suffer. And maintaining strength is precisely the metric that tells you muscle mass is being preserved.

"Your metabolism has slowed, eat more and the fat will come off"

This advice often turns up in connection with metabolic adaptation, and it sounds reassuring. But there's no evidence that increasing energy intake speeds up fat loss. Energy expenditure really does fall on a diet, but the adaptation is tens or at most hundreds of kilocalories — not enough that eating more would create a deficit. What often does work is taking a couple of weeks off at maintenance and then starting a new deficit phase. You won't burn fat during the break, but you'll restore your ability to burn it in the next phase.

Can you build muscle and lose fat at the same time?

You can, but it depends on who you are.

In beginners it often happens with ease. On his Lihastohtori ("Muscle Doctor") blog, Hulmi went through a couple of dozen strength-training studies in which fat-free mass grew by an average of roughly 0.5 kg per month in both men and women, while body-fat percentage fell at the same time by about 0.5 percentage points per month. In some of the subjects, diet wasn't touched at all.

The more experienced and leaner you are, the harder the equation becomes. At that point it's worth prioritizing and accepting that a fat-loss phase is primarily training aimed at preserving muscle mass. The old belief that muscle growth and fat loss are always mutually exclusive is worth burying in any case.

Summary

Fat loss requires an energy deficit, and there's no going over it or around it. So you can boil it down to: eat below your expenditure and burn fat.

The gym doesn't earn its place at the center of fat loss because it burns the most calories. It earns it because it decides how much of the weight you lose is fat. Strength training, enough protein, and a moderate deficit is a combination that works just as well on your first diet as on your fifth.

The fat-burning heart rate, crunches, and capsules can stay on the search results page.

Want a program that's built for you and adapts as your diet progresses? Try AITOFIT free for 9 days, no credit card required. The app has over 5,400 reviews at an average of 4.9/5.

Frequently asked questions about fat loss

What's the best heart rate for fat loss?

The fat-burning heart rate refers to about 60–70% of your maximum. At this intensity a larger share of energy comes from fat, but total energy expenditure is lower than in high-intensity training such as HIIT. For body composition, total expenditure is what matters, so there's no point chasing a particular heart-rate zone for the sake of fat loss. HIIT can still be a useful tool for fat loss, but total expenditure remains the deciding factor.

Why won't fat loss get started?

The most common reason is that your energy intake is higher than you estimate. The second most common is an unnoticed drop in everyday activity during the diet. Third, you're often measuring too short a window, because the scale swings 1–3 kilos a day. Metabolic adaptation is a real phenomenon, but rarely the reason you're looking for.

How fast can you lose fat?

A sensible pace is 0.5–1% of body weight per week. For an 80-kilo person that means 0.4–0.8 kg per week. The upper end suits you when there's plenty of excess weight, the lower end when you're already lean and trained. A faster pace increases the risk of muscle loss.

How big should the calorie deficit be?

A workable starting point for most people is 15–25% of total expenditure, in practice about 300–700 kcal per day. Leave room to tighten it, because energy expenditure falls as the diet progresses.

Can you lose fat from a specific area, like your belly?

You can't. In a meta-analysis of 13 studies and 1,158 participants, fat tissue in the trained and untrained limbs decreased equally, an effect size of −0.03. Fat is mobilized from the whole body, and the order is largely determined by genetics.

Which burns fat better, the gym or cardio?

Cardio burns more energy during the workout itself. Strength training, on the other hand, decides how much of the weight you lose is fat rather than muscle. The best result comes from a combination in which strength training is the foundation and endurance training supplements energy expenditure.

Does snacking block fat loss?

It doesn't. Meal frequency doesn't affect fat loss when total energy and protein are the same. Insulin slows the release of fat after a meal, but the day's net balance is determined by energy balance. Choose your meal rhythm by what keeps you full and lets you split your protein across 3–5 meals a day, which also supports muscle on a diet.

Should you cut carbs for fat loss?

You shouldn't. When protein and total energy are the same, a low-carb diet doesn't burn fat faster. The weight that drops quickly at the start of ketosis is largely water leaving along with your glycogen. For someone who trains at the gym, carbs support strength levels and recovery.

How much protein do you need for fat loss?

1.8–2.2 grams per kilogram of body weight per day. The upper end is justified when the deficit is severe and body fat is already low. More than 2.2 g/kg brings no added benefit. Split your intake across 3–5 meals a day; even distribution helps support muscle during an energy deficit.

Do fat burners work?

The evidence is weak. In Clark and Welch's 2021 meta-analysis, fat burners didn't produce a meaningful benefit for weight loss. Caffeine improves alertness and gym performance, which is useful on a diet, but as a fat burner it isn't worth buying.

How does alcohol affect fat loss?

Alcohol's problem isn't just the calories in the drinks — it also readily leads to eating more. On top of that, heavy use impairs recovery and health in general. So it's worth avoiding alcohol from the standpoint of both health and fat loss.

Can you build muscle and lose fat at the same time?

You can, especially beginners and those returning from a break. In strength-training studies, fat-free mass has grown by about 0.5 kg per month while body-fat percentage has fallen by about 0.5 percentage points. The more experienced and leaner you are, the harder the equation becomes.

Sources: Carlson L et al. The effects of training load during dietary intervention upon fat loss: a randomized crossover trial. 2022. Steele J et al. Long-term effects of interval versus moderate-intensity continuous training on body composition: systematic review and meta-analysis. Ramírez-Campillo R et al. A proposed model to test the hypothesis of exercise-induced localized fat reduction (spot reduction), including a systematic review with meta-analysis. Human Movement 2022. Murphy C, Koehler K. Energy deficiency impairs resistance training gains in lean mass but not strength: a meta-analysis and meta-regression. Scand J Med Sci Sports 2022;32(1):125–137. Longland TM et al. Higher compared with lower dietary protein during an energy deficit combined with intense exercise. Am J Clin Nutr 2016. Pasiakos SM et al. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss. FASEB J 2013. Siedler MR et al. Chronic thermogenic dietary supplement consumption: effects on body composition, anthropometrics, and metabolism. Nutrients 2023. Clark JE, Welch S. Comparing effectiveness of fat burners and thermogenic supplements to diet and exercise for weight loss. JBI Evid Synth 2021. Keys A et al. The Biology of Human Starvation (Minnesota Starvation Experiment) 1950. Hall KD et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet. Am J Clin Nutr 2016. Schoenfeld BJ, Aragon AA, Krieger JW. Effects of meal frequency on weight loss and body composition: a meta-analysis. Nutr Rev 2015. Hulmi J, Laakso H. Fat loss and preserving muscle mass on a diet. Lihastohtori 2016.

Author: Tapio Tulenheimo, M.Sc Exercise Science (Exercise Physiology), University of Jyväskylä | Reviewed by: Julius Granlund, M.Sc Exercise Science (Exercise Physiology), University of Jyväskylä