Browse evidence-based analysis of health-related claims and assertions
Stretching a muscle for a long time every day can actually make it grow bigger, not just more flexible.
Quantitative
For horses, longer, easier rides are better for building strong, endurance-ready muscles than short, super-hard sprints.
You can't build real muscle strength just by working out a few times—you need to stick with it for weeks, because the first few workouts just make your muscles look puffy, not stronger.
Descriptive
Doing specific stretching and movement exercises with a horse three times a week for three months can make the muscles along its spine grow a little bigger, helping it move more stably.
When people with fatty liver disease eat a lot of protein and lift weights at the same time while eating very little, they don’t get any extra muscle benefits — the two things don’t work together like they usually do.
Causal
When people with fatty liver disease do strength training for a month while eating less, they get stronger not because their muscles grow bigger, but because their brain and nerves learn to use the muscles better.
Adding protein shakes to strength training doesn’t make people with fatty liver disease any stronger or more enduring than just doing the workouts alone — even when they’re eating less food.
People with fatty liver disease on a low-calorie diet don’t lose muscle if they eat at least 0.8 grams of protein per kilogram of body weight each day — eating more protein doesn’t help any more.
People with fatty liver disease who do strength training five times a week for a month get stronger and can do more reps without getting tired, even if they’re eating less food.
In very overweight people, other genes known to affect fat and liver health didn’t change between those with mild and severe fatty liver — only SIRT1 did, making it stand out as a possible key player.
People with very overweight and severe fatty liver also have much worse insulin resistance — meaning their bodies don’t respond well to insulin — compared to those with milder liver fat.
In very overweight people, only the fat around the organs (not the fat under the skin or back) shows lower levels of a protective gene (SIRT1) when the liver is very fatty — suggesting belly fat is uniquely involved.
In very overweight people with severe fatty liver, the less SIRT1 gene activity they have in their belly fat, the worse their body’s response to insulin tends to be — meaning their blood sugar control is poorer.
Correlational
In very overweight people, those with the worst fatty liver also had much lower levels of a specific gene (SIRT1) in their belly fat, which might mean this gene helps protect the liver from too much fat.
Eating whey protein during extreme dieting might reduce the muscle’s fat-burning response to leptin, compared to eating sugar—but this isn’t proven yet.
Muscles with more slow-twitch fibers (used for endurance) tend to have stronger leptin signaling during extreme dieting, suggesting these fibers are better at switching to fat-burning mode.
When the body is in extreme calorie deficit, the arms respond more strongly to fat-burning signals than the legs—possibly because the legs make more of a protein that blocks those signals.
Even though the body starts using leptin better to burn fat during extreme dieting, it also makes more of a protein (PTP1B) that normally blocks leptin—like the body is both stepping on the gas and the brake at the same time.
When people burn a lot more calories than they eat for a few days, their muscles start responding more to a hormone called leptin, which helps them burn fat better—especially in the arms.
After a hard bike ride or run, eating lots of carbs for a few days almost always makes your muscles store more energy than before—even if the amount varies.
If your muscles already have a lot of stored energy before you start exercising, they don’t store as much extra energy afterward—even if you eat lots of carbs.
The more you deplete your muscle energy stores during a hard bike ride, the more your muscles can overfill with energy afterward when you eat carbs.
When you eat a higher percentage of your calories from carbs (like 80% vs 60%), your muscles store more energy after a hard bike ride—even if you’re eating the same total amount of carbs.
After biking really hard and then eating a lot of carbs for a few days, your muscles store way more energy than they do after running hard and eating the same way.