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Can Type 2 Diabetes Occur in Those Underweight?

A common myth surrounding type 2 diabetes is that it only occurs in people who are overweight. After all, it is known that 85% of people with type 2 diabetes are overweight.1

Can thin people develop type 2 diabetes?

The assumption is that slim people are by default healthy; they can't possibly have diabetes! The problem is further complicated by the fact that type 2 diabetes is an invisible condition. As an invisible condition, it is hard to really see that diabetes can affect anyone across all body weights.

The “skinny fat” person

Many of us have heard of the term "skinny fat"; it is used commonly to describe people who want to add bulk, or muscle mass, to their frame. What may be surprising to hear is that "skinny fat" is actually a medical condition referred to as metabolically obese normal weight, or MONW.2 A person with MONW has a normal weight and body mass index (BMI); however, are classified as metabolically obese. These people may have more visceral fat, which is the fat stored deep into the abdomen. Visceral fat is often more dangerous because it can secrete substances that impair how well insulin works.

It is impossible to determine that someone is skinny fat just by appearance alone. Medically, diagnosing MONW is difficult as there are no clear diagnostic measures.

Risks of metabolically obese normal weight

Despite having a normal body mass index, studies have determined that people who fall into the MONW category have insulin resistance and/or high blood insulin levels, high triglycerides, and high blood pressure.1 These individuals have a higher risk of type 2 diabetes and cardiovascular disease. In addition, people with MONW who also have central fat distribution, are inactive, and have a low VO2 maximum (the maximum amount of oxygen consumed during exercise), are more likely to be diagnosed with type 2 diabetes.3

Older adults with metabolically obese normal weight

A study analyzed 39,201 men and 88,012 women aged 40–79 years for 8 years to determine if there was an association between weight and developing type 2 diabetes. The study showed that there was an association with being underweight and developing type 2 diabetes. People in the study who had a BMI less than 18.5 kg/m2, which is classified as underweight, and were between the ages of 60-79 had a greater risk of developing type 2 diabetes than those in the same age group but of normal weight. However, there was no association found between being underweight and developing type 2 diabetes in people between the ages of 40-59.4

Why is this the case? Well, we know that insulin secretion declines in older adults. In addition, people who have protein-calorie malnutrition and magnesium deficiency are more likely to have low insulin secretion.5 Low dietary magnesium, which has been seen in older, underweight adults, is associated with type 2 diabetes.

The paradox

The above proves that yes, you can be thin and be diagnosed with type 2 diabetes. Which leads to another question - do thin people with type 2 diabetes fare better than those with the condition who are overweight? Turns out, that is not the case. A study following people who were diagnosed with type 2 diabetes showed those who were lean were twice as likely to pass away from diabetes complications than those who were overweight.6

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