Health Claims

When untrained young men lift heavy weights three times a week for five months, they get much stronger—some exercises more than double their original strength.

Quantitative

Taking a little longer break between sets of weightlifting (more than a minute) might help your arms and legs grow slightly bigger, but the difference is so small it might not even matter in real life.

Quantitative

The common advice to rest 30–90 seconds between sets to build muscle might need updating — resting a bit longer (over a minute) might help a little, but not enough to be sure it’s worth changing your routine.

Descriptive

When measuring overall body muscle growth with scales that can’t tell muscle from water or bone, resting longer between sets doesn’t seem to help — and might even look worse than resting shorter, but that’s probably because the measurement isn’t accurate.

Quantitative

Whether you push your muscles to complete exhaustion or stop a few reps short doesn’t change how much rest you need between sets to grow muscle.

Quantitative

Resting more than a minute and a half between sets doesn’t seem to help your muscles grow any more than resting for about a minute — after that, extra rest doesn’t add benefit.

Quantitative

Taking a bit more than a minute between sets when lifting weights might help your arms and legs grow slightly bigger, but the difference is so small it might not matter much in real life.

Quantitative

Men and women start with different hormone levels, but when they both do weight training, they gain muscle and strength at about the same rate relative to where they started.

Quantitative

If you're new to weight training, you can expect to build about 1.5 kg of muscle in the first couple of months, but after six months, your gains slow down a lot—and you probably won't gain more than 3 kg of muscle in a year unless you're using drugs.

Quantitative

When muscles get bigger over time, it’s not because the non-working parts inside them swell up—it’s because the actual muscle fibers that do the work grow more, and that’s what really matters.

Causal

Even though your muscles feel swollen and burn during a tough workout, that feeling itself doesn’t actually make your muscles grow bigger—something else must be responsible.

Causal

Even though your body releases muscle-building hormones like testosterone after a workout, those spikes don’t actually help you grow bigger muscles over time—no matter if you’re a man or woman, or whether you’re new to lifting or a seasoned athlete.

Causal

People with more active brown fat burn an extra 2% of their meal’s calories after eating carbs — which could add up to a few hundred extra calories burned per day over time.

Quantitative

Your brown fat only helps burn calories after you eat carbs — not after you eat protein or fat — which means it’s picky about what food it helps you burn.

Correlational

Eating a high-protein meal burns more calories than eating carbs or fat, but this doesn’t depend on how active your brown fat is — your body must be using other ways to burn those extra calories.

Correlational

Men and women gain muscle at about the same relative rate when they train the same way—women just start with less muscle, so they gain less in absolute numbers.

Descriptive

New lifters can expect to gain about 1–2 kg of muscle in the first few months, but after that, gains slow down dramatically—most people only add 2–4 kg per year even with years of training.

Quantitative

When muscles get bigger over time, it’s not because the non-working parts inside them swell up—it’s because the actual muscle fibers that do the contracting grow more, and that’s what really matters.

Causal

When your muscles burn and swell up during a tough workout, that feeling isn't actually what makes your muscles grow bigger—other things are responsible for the growth.

Mechanistic

Even though your body releases muscle-building hormones like testosterone after a workout, those spikes don’t actually help you grow bigger muscles over time—no matter if you’re a man, a woman, or a beginner or pro.

Causal

When you lift weights, the physical pull on your muscles is the main reason they grow bigger — not because of hormones or feeling tired or burned out.

Mechanistic

Your body burns the most calories after eating protein, fewer after carbs, and the least after fat — which is why high-protein diets are often used for weight loss.

Quantitative

Eating a fatty meal doesn’t make your body burn many extra calories, and your brown fat doesn’t seem to play any role in that process.

Descriptive

Eating a high-protein meal makes your body burn more calories afterward than eating carbs or fat, but this boost isn't linked to your brown fat — something else is responsible.

Descriptive