Insulin resistance – if you’re of normal weight or underweight you’ve probably crossed it off your list of things to worry about. After all, insulin resistance only affects people who are overweight, right? Surprisingly, the answer is no. Insulin resistance is less common in people who aren’t overweight or obese but even thin people can be insulin resistant.
The Problem of Metabolically Unhealthy Non-Obesity
You’ve probably heard about metabolically-healthy obese people, people who fall into the obese category based on BMI yet don’t suffer from the health problems associated with obesity like insulin resistance. In addition, they aren’t at greater risk for heart disease. Up to 20% of obese people fall into this category. Just as there are metabolically healthy obese people, there are a growing number of normal weight and thin people who aren’t healthy from a metabolic standpoint. They have the same metabolic issues, namely insulin resistance, that plaques overweight and obese people. These people fall into the category of “metabolically unhealthy non-obese.”
Unfortunately, people in this category are at higher risk for health problems and most are blissfully unaware of it. They look at the number on the scale and assume all is well. After all, how can they be at risk when insulin resistance is so closely linked with being overweight and obese?
Insulin Resistance in Normal-Weight and Thin People: What Causes It?
As you already know when you’re insulin resistant your cells become less responsive to the insulin your pancreas produces. Your pancreas produces insulin to help get glucose into cells. When cells lose sensitivity to insulin, the pancreas has to pump out more. As a result, people who have insulin resistance have lots of circulating insulin in their bloodstream. This overabundance of insulin further worsens the problem of insulin resistance.
Some experts believe insulin resistance is the underlying cause of most chronic health issues including heart disease, type 2 diabetes and some types of cancer. At the very least, it increases the risk for type 2 diabetes because of the stress it places on the pancreas to produce insulin. Eventually, the pancreas “tires” and can’t pump out enough insulin to take sugar into cells.
Insulin resistance is strongly linked to obesity. Having lots of fat, especially deep in your abdominal cavity, creates inflammation. Why might this be? One theory is that in obese people fat cells expand to such a large size that they can’t get enough nutrients and oxygen. When they die, immune cells come on the scene and release inflammatory chemicals called cytokines that cause inflammation. It’s still not clear which comes first – inflammation or insulin resistance but they seem to egg each other on and create an inflammatory environment. It’s this ongoing inflammation that may fuel the development of health problems like heart disease or cancer.
How Can Thin People Be Insulin Resistant?
Genetic factors put some people at risk for insulin resistance. If you have a strong family history of type 2 diabetes, you may be at higher risk even if you’re slender. Even people who aren’t genetically at risk for insulin resistance and type 2 diabetes and aren’t overweight or obese can develop insulin resistance. Your body weight says nothing about your body fat percentage or how that body fat is distributed. You’ve heard the term “skinny fat,” haven’t you? It describes people who are slender but have a high body fat percentage. If you’re of normal weight but your body fat percentage is high you may be in a pro-inflammatory state, especially if you’re fueling this inflammation by eating lots of processed foods.
The other factor that influences your risk for insulin resistance is how your body fat is distributed. If you store lots of fat deep in your abdominal area, you’re at higher risk for insulin resistance relative to someone who has less visceral fat.
How do you know if you’re carrying too much visceral fat? Usually, people with lots of visceral fat have a large waist-to-hip ratio. That’s why it’s important to know your waist measurement. A large waist-to-hip ratio is a marker for metabolic problems like insulin resistance and a higher risk for heart disease. Someone with a normal waist-to-hip ratio may be at lower risk for insulin resistance than a slender person with a high ratio and lots of hidden visceral fat.
According to recent research, your waist measurement alone says a lot about your risk for insulin resistance. For women, a waist circumference above 34 inches and 40 inches for men raises a red flag.
Other Markers for Insulin Resistance
Other signs that you may be insulin resistant include a low HDL-cholesterol level (the good kind), high blood levels of triglycerides, a high fasting blood sugar or high blood pressure. Not everyone that has one of these abnormalities is insulin resistant, but if you have more than one or two of them the likelihood goes up.
Preventing Insulin Resistance
One of the best ways to lower your risk for insulin resistance is regular exercise – resistance training and aerobic exercise. Research clearly shows exercise improves insulin sensitivity. Plus, it helps to reduce visceral abdominal fat, especially if you do high-intensity exercise. Another way to lower your risk is to eliminate processed carbohydrates and added sugars from your diet and replace them with whole foods and fiber-rich carb sources that won’t cause blood sugar spikes. Almost as important as diet is sleep. A study showed even a single night of reduced sleep can trigger insulin resistance in otherwise healthy people.
The Bottom Line?
You can be insulin resistant even if you’re not overweight. Lower your risk by working out regularly, staying active when you’re not working out, getting enough sleep and by eliminating processed carbohydrates from your diet. Insulin resistance is a common problem and no one is immune. That’s why lifestyle is so important. You can’t change the genetics you were born with but you can weaken their influence with healthy lifestyle choices.
(J Clin Endocrinol Metab 97: 2482-2488, 2012)
BMJ 2005; 330 doi: http://dx.doi.org/10.1136/bmj.38429.473310.AE
Scientific American. “Does Inflammation Trigger Insulin Resistance and Diabetes?”
QJM (2003) 96 (6): 441-447.doi: 10.1093/qjmed/hcg069
Science Daily. “One sleepless night can induce insulin resistance in healthy people”
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