The Link Between Diabetes and Obesity

By Janet B. McGill, MD, FACE
The Link Between Diabetes and Obesity

Type 2 diabetes mellitus (DM2), the diabetes that is a combination of insulin not working as well as it should in the body, plus a decreasing production of insulin by the body, is common and is now at its highest levels in U.S. history.

If you have diabetes, you already have been told that not controlling it can lead to serious complications affecting your vision, kidney function and nerve function, as well as increasing the risk for a heart attack, stroke and decreased blood flow to the legs, increasing the risk for amputation.

Those with DM2 are twice as likely to die from a heart attack or stroke than if they do not have diabetes. They are 17 times more likely to require an amputation due to decreased blood flow to the legs. And due to the delay in making a diagnosis of DM2 (as symptoms might not be present for years), kidney damage can be already seen in eight percent of patients at the time their diabetes is diagnosed and can be present in up to 40 percent of those who have had diabetes for 20 years or more. At diagnosis, 25 percent of patients with DM2 have already developed retinopathy [ret-i-nop'ă-thē], damage to the blood vessels of the retina and about two percent of the diabetic population is blind. These statistics have pushed research aimed at preventing diabetes, rather than waiting to treat the disease or its complications

And if these statistics aren’t frightening enough, diabetes challenges you every day to manage your blood sugar, your blood pressure and your cholesterol. Often, the drugs and tools required for this management can add up quite quickly, straining your budget.

Obesity is particularly associated with an increased risk of developing DM2 and is a driving factor because it triggers insulin resistance, a condition in which the body produces insulin but does not use it effectively. When people have insulin resistance, glucose builds up in the blood instead of being absorbed by the cells, leading to type 2 diabetes or prediabetes.

Both being overweight with increased abdominal fat (often described as having an “apple” shape) and being obese is thought to contribute about 80 to 90 percent of all DM2 development. Women with a BMI of 23 to 25 have a four-fold higher risk of type 2 diabetes than those with a BMI less than 20. Those with a BMI 24 to 25 have a five-fold increased risk, and a BMI over 35 increases the risk of developing type 2.

Yet clearly not all who are overweight or obese develop DM2. Additional contributing factors are ethnicity, genetics, age and maybe even a sedentary lifestyle. The development of obesity, diabetes, or both, may depend on the presence of genetic susceptibility to obesity and diabetes and perhaps also on early nutritional factors.

So what can you do if you have a risk of developing diabetes and are overweight or obese as defined by your BMI? Well....a lot!

A number of research studies have now shown that reducing body weight in overweight and obese people at high risk of developing diabetes can significantly decrease the risk of developing the disease. In a Chinese study of individuals with pre-diabetes (defined through testing these individuals by giving them a very sugary drink and then measuring their blood sugars to see if normal or high), the six-year incidence of diabetes was reduced by 36 percent in those treated with a low-fat, high-carbohydrate diet, by 47 percent through exercise only and by 39 percent through a regimen of diet and exercise.

A Swedish weight loss-intervention study looking at the effects of weight loss surgery for very obese individuals showed a two-year incidence of diabetes of six percent in those not receiving the surgery (whose weight loss was zero), compared to only 0.2 percent in those treated by surgery and who lost weight. Most of this benefit was still present at 10 years post-surgery, when the incidence of diabetes was still five-fold lower in those having had the surgery, corresponding to an 80 percent protection.

The U.S. Diabetes Prevention Pilot Program showed that, with a combination of weight loss of about seven percent accompanied by about 150 minutes a week of exercise, the risk of developing DM2 in those identified as "at-risk" decreased by 58 percent in three years.

What, then, can you do if you already have been diagnosed with diabetes? Data shows that a 15 to 20 percent weight loss in the first year after diagnosis of DM2 has been shown to reverse the excess mortality of being overweight and having DM2. A deliberate weight loss of just one to 19 pounds has been shown to be associated with a 30 to 40 percent reduction in diabetes- related mortality. And your need for medication will also be decreased; whether pills to treat high blood sugar or insulin, weight loss is associated with lower doses needed to treat your DM2. Even medication for the control of high blood pressure or high cholesterol can often be decreased with weight loss.

This is all helpful, positive information, yet it contrasts with the published scientific concept known as “obesity paradox,” which suggests that weight gain is associated with a decreased risk of early death if you have DM2. As with many studies in medical science, findings need to be repeated and repeated and repeated through different researchers looking at the same question. Hence, a very recently published study looking at over 11,000 individuals having DM2 over 16 years' time and the effects of the disease on their health over that time showed that the “obesity paradox” just does not hold. Not surprisingly, the researchers reported that those with DM2 who were overweight or obese when diagnosed with diabetes, were more likely to have died than those at the higher end of normal weight. In particular, if you were diagnosed with DM2 before age 65 and gained weight, your mortality risk was higher than if you were over 65 years at DM2 diagnosis and gained weight. And another similar study examining federal government data reported that being obese was associated with “at least” a 20 percent increased risk of early death. Those between ages 45 to 64 years old and defined as obese had a life span of seven years less than those in the normal weight category.

A deliberate weight loss of just one to 19 pounds has been shown to be associated with a 30 to 40 percent reduction in diabetes-related mortality.

So what should be the take home message? It’s a simple one: Cut your portion sizes down, walk away from tempting snacks and unhealthy food, and take a walk around the block when you get home!

Dr. Janet b. McGill Professor of Medicine and Fellowship Director in the Division of Endocrinology, Metabolism and Lipid Research at Washington University school of Medicine in St. Louis, Missouri and attending physician at Barnes-Jewish Hospital in St. Louis. She is nationally and internationally known for her work in clinical and translational research in type 1 and type 2 diabetes and diabetes complications. She has been the principal investigator and co-investigator or sub-investigator on over 200 clinical trials in diabetes, hypertension, hyperlipidemia, diabetic nephropathy and diabetic neuropathy.