Browse evidence-based analysis of health-related claims and assertions
For adults with unhealthy cholesterol levels, cutting carbs and calories for 12 weeks might improve heart disease risk more than a low-fat diet, based on deeper blood fat measures.
If you're an adult with a certain type of unhealthy cholesterol, cutting carbs while eating fewer calories might help you lose more weight and body fat over 3 months than cutting fat instead — the type of food you restrict could matter for how your body changes.
For adults with unhealthy cholesterol levels, cutting carbs while eating fewer calories seems to improve heart-related blood fats more than a low-fat diet over 12 weeks.
For adults with a certain type of unhealthy cholesterol and blood sugar issues, cutting carbs way down for 12 weeks might lower insulin and blood sugar more than a low-fat diet — meaning it could help control blood sugar better.
If you're an adult with obesity and you eat fewer carbs on a low-carb diet, you might lose more weight and see better cholesterol numbers in just a few months.
Eating fewer carbs might help boost good cholesterol and lower blood fats in people with higher body weight, but it doesn’t seem to change overall or bad cholesterol much.
Eating fewer carbs might help lower blood pressure a little bit over time, especially in people who are overweight.
Low-carb diets help people with obesity lose a little weight at first, but the benefits fade after a year, so they might not work well for keeping weight off long-term.
In rural Chinese women, eating more carbs seems to have a bigger effect on raising blood pressure for those who already have high blood pressure.
Most rural adults in China get the majority of their carbs from processed grains like white rice and white bread, and women tend to eat even more of these than men—meaning their diets may be low in fiber and not very healthy overall.
Eating more or less carbs doesn’t seem to affect blood pressure in adult men living in rural China, no matter their age, weight, salt intake, or other habits.
For women in rural China, eating too few or too many carbs might raise blood pressure, but having around 130 to 150 grams of carbs a day seems to be the sweet spot for keeping it lowest.
Eating more carbs might raise blood pressure in rural Chinese women, especially for those already at higher levels — like adding 50 grams of carbs a day could bump up blood pressure by nearly 2 points.
If young, healthy guys at rest drink salty water (with 0.7% or 0.9% salt), they hold onto more fluid than if they drank plain water—because they pee less and their body fluids stay balanced.
Drinking salt water (with a little salt) can boost blood volume in healthy young guys at rest, and the effect starts within an hour and lasts. Plain water doesn’t do this because it makes you pee more and dilutes your blood.
Drinking a sports-type drink with carbs and salt boosts blood volume faster than drinking salt water alone — it starts working in 30 minutes instead of 60, at least in healthy young guys just sitting around.
When healthy guys eat a diet high in carbs for a couple of weeks, their bodies initially hold onto more salt—but by week two, a key hormone that controls salt goes down, which might help stop blood pressure from rising.
Eating a lot of carbs for two weeks doesn’t raise blood pressure in healthy guys, even though it changes how their bodies handle salt.
When healthy guys eat more carbs for a few days, their bodies hold onto more salt at first, but this doesn’t last past the first week.
Eating fewer carbs might raise your 'good' cholesterol a little, especially if you replace them with fats or proteins, but it could also raise your 'bad' cholesterol, so it's not clear if this is truly helpful for your heart.
If adults swap carbs for saturated fats—like butter or fatty meats—it changes their cholesterol levels in different ways. The kind of food replacing the carbs matters more than just cutting carbs alone.
Eating fewer carbs—especially very low amounts—seems to lower blood fat levels more than eating a little more carbs, which might be better for heart health.
Eating very few carbs—like on a strict keto diet—can raise your 'bad' cholesterol, especially if you're replacing those carbs with lots of saturated fats like butter and red meat.
Eating fewer carbs—like bread, pasta, and sugar—might help you lose about 3 pounds on average compared to eating a normal amount, especially if you're overweight. It could be a helpful short-term strategy to manage your weight.