Have you been told you have prediabetes? A 12-week study found a surprising blood sugar benefit from lifting weights twice a week

After three months of resistance training, 34% of participants in a US trial were no longer prediabetic. They trained twice a week.

The trial is called Resist Diabetes. Brenda Davy and Richard Winett of Virginia Tech were its principal investigators. PLoS ONE published the results in February 2017.

The study enrolled 170 adults aged 50 to 69. All were sedentary, overweight or obese, and had prediabetes.


The researchers counted someone as prediabetic with a fasting glucose of 95 to 125 mg/dl, a two-hour glucose of 140 to 199 mg/dl, or both. Many guidelines start the fasting range at 100. A lower cutoff lets slightly more people in. It also changes what counts as "no longer prediabetic."

Younger, leaner or already active people weren't part of this trial. The results describe one group.

Each session had 12 sets. A set is a block of repetitions of one exercise. Two sessions a week for 12 weeks adds up to about 24 sessions.

Posts about the study mention leg presses and chest presses on weight machines.

The first three months were supervised. Participants then kept training at a gym of their choice. The last six months involved no contact with the researchers. Tests came at the start and at months 3, 9 and 15.

What a 34% reversal means

It means glucose readings fell below the study's thresholds. That's a lab result. It isn't a cure, and the paper doesn't call it one.

The number is about one in three. Whether that's large depends on what you compare it to, and this trial has limits there.

The gain mostly held. At 15 months, 30% still had normal glucose, and 76% of participants were retained. People who dropped out may differ from those who stayed. The abstract doesn't settle that.

Nobody in the study did a cardio program. Claims that weights beat cardio come from somewhere else.

There was also no group that skipped exercise during the first three months. Everyone lifted. Randomization came afterward, when participants were split into two kinds of maintenance support. Of the 170 who began, 159 were randomized. Neither maintenance approach did better than the other.

That design leaves a gap. The study can't separate the effect of lifting from other things that change in a trial. Blood sugar varies from test to test. People who join a study often change their habits.

Why muscle matters for blood sugar

Skeletal muscle is a major place glucose goes after a meal. Working muscle burns it for fuel. Regular training tends to make muscle respond better to insulin.

That's general physiology. It isn't something this trial's main measures, glucose status and strength, were built to prove.

Prediabetes often involves insulin resistance. Cells respond poorly to insulin, and sugar stays in the blood. A 2016 paper from the same project found that the type of prediabetes affected how much glucose control improved. Results varied from person to person.

The paper reports four serious adverse events. The abstract doesn't say whether training caused them.

The first three months were supervised. Starting alone, with no coaching on form or load, is a different situation.

Anyone with prediabetes should check with a doctor before starting. That's especially true with heart problems, joint pain or high blood pressure. A fasting glucose test or a two-hour test shows where you stand now.

About one in three people tested out of prediabetes after 12 weeks of lifting. Fifteen months after the trial began, three in ten still had normal glucose.

Normal, Prediabetes and Diabetes

A single blood test can place someone in one of three groups. The labels depend on cutoffs, and the cutoffs depend on who wrote the guideline.

Prediabetes isn’t an official diagnosis. It’s a designation for people with impaired fasting glucose, impaired glucose tolerance, or both. Both terms mean blood sugar that’s high but hasn’t reached the diabetes range.

Most people feel nothing.

A fasting glucose test shows what’s in the blood after a night without food. Labs want at least eight hours of fasting.

The glucose tolerance test asks how the body handles a sugar load. You drink a measured dose, then the lab checks your blood two hours later.

A1C looks backward. It reflects average blood sugar over roughly the past two to three months, so one skipped dinner won’t change it.

The American Diabetes Association (ADA) puts prediabetes at 100 to 125 mg/dL for fasting glucose, 140 to 199 for the two-hour test, and 5.7% to 6.4% for A1C.

Diabetes begins at 126, 200 and 6.5%. Anything below the prediabetes range counts as normal.

Meeting one of those criteria is enough to land in a category.

The WHO and the International Diabetes Federation start impaired fasting glucose at 110 mg/dL, not 100. India’s RSSDI guidelines use 110 too.

A fasting reading of 105 is prediabetes under the ADA. Under the WHO, it’s normal.

Neither is wrong. Blood sugar risk rises gradually, and each body draws its line on a sliding scale. The Resist Diabetes trial used 95 as its entry point, lower than either.

Doctors are careful about labeling someone. Without obvious symptoms, a diabetes diagnosis needs two abnormal results, either from the same sample or from two separate tests.

A random reading of 200 or higher counts by itself only when classic symptoms are present. Those symptoms are heavy thirst, frequent urination and unexplained weight loss.

A1C has limits. It shouldn’t be used to diagnose in pregnancy or with marked anemia. Glucose tests decide in those cases.

Type 1: an immune system problem

Type 1 is autoimmune. The immune system destroys the cells in the pancreas that make insulin. The body ends up with little or none.

People with type 1 need insulin from outside for life. It often starts in childhood or young adulthood, but it can show up at any age. Food and body weight don’t cause it.

Symptoms tend to arrive quickly. For some people, the first sign is a medical emergency called diabetic ketoacidosis.

Type 2: the body stops responding

Type 2 works differently. The pancreas still makes insulin, but cells respond to it poorly. That’s insulin resistance.

For a while, the pancreas makes extra to compensate. Over time it can’t keep up, and glucose climbs.

Risk rises with excess weight, inactivity, age and family history. The process is slow and can run for years before anyone is diagnosed.

Some people manage it with food and activity. Others need tablets or insulin.

Gestational diabetes is a third category. It’s glucose intolerance first recognized during pregnancy.