Cholesterol and heart health benefits
Varady notes that the weight-loss benefits of fasting can help with “lowering metabolic disease risk indicators like blood pressure and cholesterol levels.” A small 2025 six-month intermittent fasting trial shows “improvements in triglycerides and LDL/non-HDL cholesterol,” says Fontana, who co-authored the study.
These improvements occur, in part, because weight loss reduces visceral (abdominal) fat and decreases the liver’s production of fat-carrying particles that circulate in the bloodstream—both of which positively affect lipid profiles.
Mattson adds another potential mechanism at play for reducing blood pressure: “Intermittent fasting increases the activity of the parasympathetic nervous system,” he says. This branch of the nervous system helps the body relax, digest food, and conserve energy after periods of stress or activity, and greater parasympathetic activity can lower heart rate, reduce vascular resistance, and counteract chronic sympathetic “fight-or-flight” activation that’s associated with hypertension.
Again though, there are caveats. “Improved cholesterol and blood pressure generally only occurs if an individual loses over 5 percent of their body weight and if their blood pressure and cholesterol levels were high before starting the diet,” says Varady.
Blood sugar and diabetes: Real potential and real risks
Research also shows that fasting can influence glucose regulation. This occurs partly because fasting lowers circulating insulin levels, increases insulin sensitivity, and shifts the body toward greater fat oxidation and ketone production—meaning the body begins burning stored fat for energy instead of relying primarily on glucose from recently eaten carbohydrates.
Mattson says intermittent fasting can also enhance cellular stress resistance, stimulate autophagy—a natural cellular “cleanup” process in which the body breaks down and recycles damaged or unnecessary components—and improve mitochondrial function. Together, these changes may improve glucose regulation and the body’s ability to maintain stable blood sugar and metabolic balance during periods of stress, illness, or dietary changes.
Other studies show additional benefits for people with insulin resistance or type 2 diabetes in particular, including reductions in fasting glucose, lower hemoglobin A1c levels, decreased visceral fat, and, in some cases, reduced need for diabetes medications.
(Can fasting help you live longer? Here’s what the science says.)
Still, fasting is not risk free for people with diabetes. Mellor warns that “people who take insulin or drugs that cause the body to make more insulin should speak to a doctor before starting a fasting diet,” largely because hypoglycemia remains a real risk if medications are not adjusted appropriately.
Brain benefits and mental health
Many people also report sharper thinking or improved mood while fasting, but “clinical trials have not been able to show the same benefits” in healthy individuals, says Mellor. At the same time, research does show benefits of intermittent fasting for people with epilepsy, Alzheimer’s disease, and multiple sclerosis—both in terms of symptoms and disease progression.