It's often assumed that in order to develop type 2 diabetes, you have to be overweight. While it's true that excess weight is clearly associated with insulin resistance and diabetes, it's the insulin resistance — not necessarily the weight gain — that drives the disease.
As such, many people with a healthy weight are not metabolically healthy, putting them at risk of diseases like type 2 diabetes — even without being overweight or obese.
One of the greatest risk factors, according to University of Florida researchers, is actually inactivity, which drives up your risk of pre-diabetes regardless of your weight.
Inactivity Is Associated With Pre-Diabetes, Even if You're a Healthy Weight
If you were looking for motivation to get moving, this study, published in the American Journal of Preventive Medicine, is as good as it gets.1
In a survey of more than 1,100 healthy-weight individuals, those who were inactive (physically active for less than 30 minutes per week) were more likely to have an A1C level of 5.7 or higher, which is considered to be pre-diabetic.
Among all the inactive participants (aged 20 and over), about one-quarter were either pre-diabetic or diabetic. When only those inactive people aged 40 and over were analyzed, the percentage rose to 40 percent.
The researchers suggested that people who live a largely sedentary lifestyle yet have a healthy weight may have "normal-weight obesity or 'skinny fat,'" which they described as a "high proportion of fat to lean muscle."2
"Don't focus solely on the scale and think you're OK. If you have a sedentary lifestyle, make sure you get up and move," lead author Arch Mainous III, chair of health services research, management and policy in the University of Florida's College of Public Health and Health Professions, said in a news release.3
The researchers also noted that their findings suggest "healthy weight individuals may benefit from physical exercise,"4 which isn't exactly groundbreaking advice — but it's incredibly important nonetheless.
Weight Doesn't Always Reveal a Person's Metabolic Health
Weight isn't always an accurate tool by which to gauge metabolic health, and research by Dr. Robert Lustig, professor of pediatric endocrinology at the University of California, San Francisco (USCF), bears this out.
Lustig is perhaps best known for speaking out about the health risks of sugar, but in our 2015 interview he explained the problem with "judging a book by its cover" in terms of weight and health.
More than two-thirds of the American population is overweight or obese. About 50 percent have diabetes or pre-diabetes,5 and 1 out of every 3 have high blood pressure.6 Many also have high serum triglycerides, which is a risk factor for heart disease and stroke. Insulin resistance is a component of all of these health issues.
According to Lustig, at least 50 percent of Americans have some form of insulin resistance — whether you're overweight or not — and that is what's driving our seemingly out-of-control disease statistics.
'There Are More Thin Sick People Than Fat Sick People'
As Lustig notes, if you were to do a Venn diagram of the U.S. population, one circle would be about twice as big as the other: the obese population forming a smaller circle of about 30 percent, and the non-obese population forming a larger circle of about 70 percent.
He estimates that about 80 percent of the obese population is metabolically ill with insulin resistance that manifests itself in a myriad of ways, including type 2 diabetes, hypertension, dyslipidemia, heart disease, cancer and dementia. About 20 percent of this population, however, is metabolically healthy.
Conversely, Lustig explains, of the 70 percent that are of normal weight, about 40 percent of them have insulin resistance upon lab testing, and they manifest aspects of metabolic syndrome as well. They too get type 2 diabetes, hypertension, dyslipidemia, cardiovascular disease, cancer and dementia.
The prevalence of metabolic disease among normal-weight people is not as great as among obese people — 40 percent versus 80 percent — but there are far more people in this group.
"When you do the math, there are more thin sick people than there are fat sick people," Lustig says. And while his research points to excessive sugar consumption as the primary driver of metabolic disease among Americans, inactivity also plays a role.
Exercise Is Important, but Not Necessarily Because It Helps You Lose Weight
The evidence is clear that regular physical activity, which includes reducing your time spent sitting and exercising, is crucial to lower your risk of diabetes (and treat it if you've already been diagnosed).
For instance, sitting for more than eight hours a day has been shown to increase your risk of type 2 diabetes by 90 percent,7 while people with diabetes who engaged in a six-month moderate-intensity exercise program experienced significant health improvements, including decreased fat in the abdomen, liver and around the heart.8
Many health care professionals advise their patients to exercise in order to promote weight loss; however, its benefits extend far beyond that (which is why it's important to exercise even if you don't need to lose weight).
According to Lustig, one of exercise's primary benefits is that it promotes muscle gain and stimulates peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1 alpha), which is the primary driver for mitochondrial biogenesis.
When you turn up PGC-1α, you make more mitochondria, increasing your sympathetic muscle tone, which in turn improves insulin sensitivity. According to Lustig:
"Exercise is the single best thing you can do for yourself and we should be promoting it, but we have to explain to patients what the outcome variable they should be looking at is.
And the outcome variable is belt size [waist size], because they will reduce their visceral fat. They will lose inches, not pounds. And losing inches means improved metabolic health."
How to Determine if You're Pre-Diabetic
If you're reading this and aren't sure what your fasting insulin and glucose levels are, these are blood tests I recommend receiving annually. Your fasting insulin level reflects how healthy your blood glucose levels are over time.
A normal fasting blood insulin level is below 5, but ideally you'll want it below 3. A fasting glucose level below 100 mg/dl suggests you're not insulin resistant, while a level between 100 and 125 confirms you have pre-diabetes. If this, or your A1C level, confirms you either have or are at risk of pre-diabetes or diabetes, the time to take action is now. You might also find a hip-to-waist size index chart helpful.
This is far better than body mass index (BMI) for evaluating whether or not you may have a weight problem, as BMI fails to factor in both how muscular you are and your intra-abdominal fat mass (the dangerous visceral fat that accumulates around your inner organs), which is a potent indicator of insulin/leptin sensitivity and the associated health problems.
You Can Improve Your Insulin Sensitivity in Just Two Weeks
Fortunately, proper exercise and attention to diet can reverse the course of this disease, with benefits seen in as little as two weeks (and to some extent after just one exercise session).
For instance, unfit but otherwise healthy middle-aged adults were able to improve their insulin sensitivity and blood sugar regulation after just two weeks of interval training (three sessions per week).9 A follow-up study also found that interval training positively impacted insulin sensitivity.
The study involved people with full-blown type 2 diabetes, and just one interval training session was able to improve blood sugar regulation for the next 24 hours.10 You can actually reap much greater benefits by exercising in short, high-intensity bursts known as intervals than you can exercising for longer periods at a slower steady pace.
The high-intensity interval training (HIIT) approach I personally use and recommend is the Peak Fitness method, which consists of 30 seconds of maximum effort followed by 90 seconds of recuperation, for a total of eight repetitions. I also recommend super slow weight lifting for your resistance training.
Getting Up From Your Chair Is Also Important
When you hear the term sedentary, it's important to understand that exercising for 20 or 30 minutes a day, and then sitting for much of the rest, is not enough to pull you out of this category. Long hours spent sitting are linked to chronic diseases including diabetes, and this may be, in part, because it increases aging at the cellular level.
In a study of 64- to 95-year-old women, those who sat for more than 10 hours a day and got less than 40 minutes of moderate-to-vigorous physical activity had shorter telomeres and were, on average, eight years older, biologically speaking, than women who moved around more often.11
Every time a cell divides, the telomeres get shorter, which is why they're used as a measure of biological aging. Short telomeres have also been linked with chronic diseases such as cancer, heart disease and diabetes.
In addition, your body's ability to respond to insulin is affected by just one day of excess sitting, which leads your pancreas to produce increased amounts of insulin. Research published in Diabetologia also found that those who sat for the longest periods of time were twice as likely to have diabetes or heart disease, compared to those who sat the least.12 I recommend replacing the majority of your sedentary sitting time with active movement, keeping sitting to three hours a day or less.
What to Do if You Have Pre-Diabetes or Diabetes
The take-home message to remember is that you shouldn't assume you're metabolically healthy just because you're not overweight or obese — especially if you live a largely sedentary lifestyle. You could actually be "skinny fat," with many of the same health risks as someone who's overweight or obese and sedentary.
The good news is that there's plenty you can do to not only reduce your risk of type 2 diabetes and pre-diabetes but also improve your metabolic health at the same time.
During the three-year Diabetes Prevention Program study, for instance, lifestyle interventions were found to be more effective than the diabetes drug metformin at preventing or delaying the development of diabetes in people at high risk of the disease. A follow-up study monitored the group for 15 years — and lifestyle interventions were still more effective than metformin at preventing diabetes.13
After the initial three-year study, those who made dietary changes and exercised at moderate intensity for 15 minutes daily were 58 percent less likely to develop diabetes compared to a placebo group. Those taking metformin were 31 percent less likely to develop the disease. Nutrition and lifestyle modifications should be the foundation of your diabetes prevention and treatment plan.
Remember, this is about getting metabolically healthy, not necessarily losing weight, but optimizing your weight is a pleasant "side effect" that comes from a healthy lifestyle.
One of the most important dietary recommendations is to limit net carbs (total carbohydrates minus fiber) and protein, replacing them with higher amounts of high-quality healthy fats, like seeds, nuts, raw grass-fed butter, olives, avocado, coconut oil, organic pastured eggs and animal fats (including animal-based omega-3s).
If you're insulin resistant or diabetic, I also strongly suggest you limit your total fructose intake to 15 grams per day until your insulin/leptin resistance has resolved (then it can be increased to 25 grams) and start intermittent fasting as soon as possible.
As mentioned, exercise and reduced sitting time are also crucial, along with attention to proper sleep, optimized vitamin D levels and gut health. Taken together, this plan will lower your risk of diabetes and related chronic diseases and help you to avoid becoming victim to a health condition you might not even realize you have.