Browse evidence-based analysis of health-related claims and assertions
People with thicker arms—likely indicating more muscle and healthy fat—are less likely to die early, even after accounting for their overall weight or belly fat.
Correlational
A new body shape score called ABSI—which considers waist size relative to height and weight—can help predict who’s at higher risk of dying early, even if they’re not obviously overweight.
If your waist is more than half your height, you’re at much higher risk of dying early—this ratio is a better warning sign than just your weight or BMI.
People with bigger waists are more likely to die sooner, even if their overall weight seems normal—this means where you carry fat matters more than how much you weigh.
Whether you do full or half curls, your arms still get stronger and a bit bigger—so you don’t need to do one over the other to see results.
Descriptive
Whether you do full or half curls, the upper part of your bicep grows about the same amount—so where you curl doesn’t matter much for that part of the muscle.
Quantitative
Doing bicep curls only halfway up might help you push harder when your arm is bent at 100 degrees, even though you didn’t train that angle—possibly because your muscle got a bit bigger in the stretched part.
Doing full bicep curls might help you lift a little more weight in a max lift than doing half curls, but the difference is tiny and not very certain.
Doing bicep curls only halfway up (keeping the arm stretched) might make the lower part of your bicep grow a tiny bit more than doing full curls, but the difference is very small.
WWI might be better because it catches people who are skinny but have a big belly and weak muscles, which is more dangerous for the heart than just being overweight.
Mechanistic
Measuring just waist size or blood fat levels alone isn’t as good at predicting heart disease risk in people with metabolic problems as using a combined measure like WWI.
WWI is especially good at spotting heart disease risk in younger people and those who already have diabetes, high cholesterol, or metabolic syndrome.
WWI is the best simple body measurement for spotting who’s at risk of heart disease among people with metabolic problems—even better than BMI or waist size alone.
A measure combining waist size and blood fats (CMI) predicts heart disease risk—but only up to a certain point; beyond that, higher values don’t mean higher risk.
People with a large waist relative to their body weight are more likely to have a heart attack or stroke later on, even when you account for other health problems like diabetes or high blood pressure.
Helping people change their habits works better when you meet them where they are—whether they’re just thinking about it or already trying—instead of giving them the same advice everyone gets.
Causal
People who are overweight but also have weak muscles and low strength are at much higher risk of falling, breaking bones, and dying early than people who are just overweight or just weak.
New weight-loss drugs like Ozempic and Mounjaro cause you to lose a lot of muscle and may weaken your bones, even though they help you lose weight fast.
Going on a very strict diet with very few calories can hurt your bones more than a moderate diet—even if you’re eating enough protein and calcium.
Eating more protein (about 1.2 to 1.6 grams per kilogram of body weight) while dieting helps you keep your muscles and doesn’t hurt your bones.
Doing strength exercises like lifting weights while losing weight helps keep your muscles and bones strong, unlike just walking or cycling, which can make you lose more muscle and bone.
In obese animals, the fat tissue grows too fast for blood vessels to keep up, so parts of the fat don’t get enough blood and oxygen, which may trigger problems like inflammation and insulin resistance.
In obese animals, fat cells with low oxygen may have fewer and less efficient power plants (mitochondria), making them worse at burning energy and possibly worsening insulin resistance.
When fat cells are starved of oxygen, they get stressed inside, which may interfere with how they respond to insulin and make metabolic problems worse.