Browse evidence-based analysis of health-related claims and assertions
When scientists turned down the activity of certain brain cells in mice that use acetylcholine, the mice ate way more and got very fat; when they turned the cells up, the mice ate less.
Correlational
Nicotine works better at making mice eat less when they’re eating fatty, unhealthy food — suggesting that what you eat changes how nicotine affects your appetite.
Descriptive
When mice can choose when to get nicotine (like smoking), they don’t eat less or lose weight on normal food — but they do if they’re on junk food, showing nicotine’s effect depends on what and when you eat.
Nicotine might make the brain think food is less filling than it really is, because it keeps the 'hunger signal' active even when you see food — so your brain doesn't realize you're about to eat and you eat less.
Mechanistic
When scientists remove a specific part of the nicotine receptor in the hunger center of mice brains, nicotine can no longer make them eat less — proving that part is essential for suppressing appetite.
Nicotine makes two types of brain cells in the hunger center fire at the same time — one that says 'eat' and one that says 'stop eating' — which confuses the brain and leads to eating less.
People who smoke tend to weigh less than non-smokers, and when they quit, they usually gain about 4 kg because their body goes back to how it normally weighs without nicotine.
When young rats were given sugar water, their blood sugar, insulin, and fat levels didn’t change whether they had nicotine or a fake pellet.
Even when young rats got nicotine, they didn’t gain more or less weight than rats that got a fake pellet — as long as they all ate the same amount of food.
Giving young rats nicotine through a pellet didn't change their leptin hormone levels, whether they had eaten or just drunk sugar water.
Even though older brains still get enough oxygen, their blood flow isn’t good at removing waste like carbon dioxide and acid, which might be the real reason thinking slows down with age.
About 1 in 8 older adults have a buildup of carbon dioxide in their brain that’s large enough to disrupt normal brain wave patterns and thinking, based on previous research.
Quantitative
In older brains, the areas most involved in thinking, planning, and movement (like the front of the brain and deep structures) are the ones most affected by both too much carbon dioxide and too little oxygen.
Older brains get less oxygen in their tissues because of reduced blood flow, and in about 1 in 8 older people, this drop is big enough to potentially affect thinking and vision.
As people get older, their brain gets less blood flow, which makes it harder to clear out carbon dioxide waste, leading to slightly more acidic conditions in the brain that might slow down thinking and memory.
Instead of telling these players to eat more protein, nutritionists should focus on getting them to eat more carbs — especially on game days — because they’re not eating enough total calories.
These players eat more protein than most people need — about 1.9 grams per kg of body weight — but they might not need that much, especially if they’re not eating enough carbs.
These players eat more carbs on game days and training days than on rest days — they’re eating more fuel when they need it most.
These female pro soccer players eat about 2,300 calories a day, but they burn nearly 3,000 — meaning they’re likely not eating enough to keep up with their training.
Female pro soccer players burn about 2,900 calories a day, mostly from playing and training, and the more muscle they have, the more calories they burn.
As countries have shifted from eating whole foods to eating packaged, processed foods, their rates of obesity have gone up at the same time — a pattern seen around the world.
Processed foods often contain artificial sweeteners, chemicals to make them smooth, and toxins from packaging, which might interfere with how your body regulates hunger and fat storage.
Eating a lot of processed foods may change the good bacteria in your gut in ways that make it harder for your body to manage weight and blood sugar.
Foods like cookies, chips, and sugary cereals are designed to be eaten quickly and taste super good, so people eat more before feeling full than they do with whole foods like fruits or beans.