Fasting also isn’t exactly fun and can be harmful for some people. Since you’re restricting food intake, that comes with all the usual side effects like low energy, lightheadedness and being hangry. If you’re healthy and determined to try fasting, you may be able to adjust to it, but for people with existing medical conditions, it could be dangerous.
“It’s a bad idea for anyone who’s pregnant, is elderly or has a medical condition that involves taking medication, such as high blood pressure or diabetes,” Lynch says. “It’s also dangerous territory for people with eating disorders.”
Fasting to help with diabetes
There have been some human case studies that have generated buzz because they suggest intermittent fasting can help people prevent or manage diabetes. But a majority of fasting research has been conducted with rats, and rats are, obviously, different from humans in a lot of ways. More research is needed to determine if fasting has a significant impact on human health.
Fasting could be helpful for some people who have prediabetes or type 2 diabetes, at least in theory, Lynch says.
That’s because of the relationship between diabetes and insulin, the hormone that makes it possible for sugar in our blood to enter our cells and be used or stored for energy. The greatest need for insulin is after eating, especially after a high-carb meal.
People with type 2 diabetes, however, are often resistant to the effects of insulin, meaning their bodies don’t use it efficiently or make enough extra insulin to digest carbs. This causes their blood sugar levels to rise and triggers other metabolic changes that increase their risk for heart disease, stroke and other serious medical problems.
Fasting, however, might reduce carb intake and lower blood sugar levels. This, in turn, reduces the need for insulin and may help decrease someone’s risk for harmful metabolic changes associated with high blood sugars.
“This is where things like low-carb diets come into play, by mitigating insulin response to allow insulin levels to normalize. Intermittent fasting is like the next variation of that,” he says.
Fasting is not a replacement for medication, however, and if you have diabetes it isn’t safe to try fasting without first consulting with your doctor or dietitian.
“You’ll most likely need to adjust medications on some level,” he says. “Many of them are meant to be used with food, so if you take food out of the equation, you could have lots of low blood sugars.”
It also isn’t a long-term solution, because what someone with diabetes eats is critical, not just when they eat.