Your muffin top’s messing up more than your bikini pics.

New research links belly fat to a host of scary medical issues, including heart disease, stroke, Type 2 diabetes and cancer — even if you’re at a normal weight.

According to the study, which was conducted as part of the National Institutes of Health’s ongoing Women’s Health Initiative and published in JAMA Network Open medical journal, postmenopausal women of a normal weight are at a 31% higher risk of death if they also have excess belly fat — a similar risk level to that of obese individuals.

Most of us have an idea of what excess belly fat looks like: a spare tire on dudes, or an apple-shaped body on women. But Dr. Rekha Kumar, endocrinologist at Weill Cornell Medicine and NewYork-Presbyterian, says that the sneaky fat can be harder to detect than you might think.

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“Somebody might not look overweight . . . or even look like they have a big beer belly,” she tells The Post. “But some people are genetically prone to storing more fat around the belly.”

Rather than tracking overall weight, Kumar says that individuals should be focusing on their waist-to-hip ratio — the number you get when you divide the circumference of your waist by the circumference of your hips. It’s the “fourth vital sign, after temperature, pulse and blood pressure,” in Kumar’s opinion. Ideally, Kumar explains, your waist should be notably smaller than your hips.

She points to a past study published in the Medical Journal of Australia that found those measurements to be the most crucial predictor of cardiovascular death — even more so than body-mass index and your actual waist circumference. Men and women whose waist-to-hip ratio was more than 0.90 or 0.80, respectively — meaning, those who tended to have waists close to or bigger than the width of their hips — had higher mortality rates.

Although Kumar hopes primary care physicians will begin monitoring the ratio in their patients, it’s not currently common practice for most docs. So she suggests doing it at home instead: Simply measure your waist and hips with a tape measure, then divide the circumference of your waist by that of your hips. For example, someone with a 28-inch waist and 38-inch-wide hips has a healthy ratio of 0.74.

Getting belly fat under control can be difficult, especially for aging individuals whose metabolism slows over time, but there are straightforward ways to tackle the issue. Kumar suggests starting with a diet cleanup, cutting out highly processed foods and focusing on “a low-carbohydrate, no-added-sugar approach,” with plenty of whole foods.

Then, hit the gym — but do it right: Certain types of exercise are more effective than others for belly pudge, says Kumar. Instead of cardio, she says to focus on resistance and weight training, both of which have shown a correlation with reduced waist circumference.

Here are a few other quick tips from Kumar for busting belly flab.

• You don’t need to go nuts at the gym — but do try holding a plank pose for at least one minute per day. This simple move engages the whole core and strengthens abs, says Kumar.
• Get some sleep. Kumar says not getting enough shut-eye “leads to an increase in cortisol, our stress hormone, which promotes belly fat storage.”
• Cut back on booze. “People forget that alcohol is actually a toxin, so when our body is breaking down alcohol, it’s usually not breaking down body fat — because our liver is busy,” says Kumar.