The Lesser-Known Consequences of Obesity

Kathleen l. Wyne, MD, PhD, FACE
The Lesser-Known Consequences of Obesity

When we hear about obesity on the news, the discussion is usually focused on the risk of diabetes and heart attacks for very obese people, usually in the range that is now called Class 3 (high-risk) obesity, formerly called “morbid obesity.” The dialogue rarely addresses the fact that the risks of complications start prior to the onset of Class 3 obesity and also when overweight, which is a BMI —body mass index—of 25-30

What many don’t know is that obesity is an established risk factor for a number of serious medical conditions, including not only diabetes and heart disease, but also chronic kidney disease, heart failure, neuropathy, asthma, arthritis and cancer.


Chronic Kidney Disease (CKD) may develop prior to the onset of diabetes in the obese patient and can be diagnosed from a simple blood test called serum creatinine [kre-at-i-nin]. Serum creatinine is typically measured as part of a comprehensive metabolic panel, a group of 14 blood tests that provide an overall picture of your body’s chemical balance and metabolism, and should be measured at least annually in people who are obese. A glomerular filtration rate (GFR) is then calculated from the serum creatinine; this is a test that measures how well the kidneys are working and specifically estimates how much blood per minute is passing through tiny glomeruli in the kidneys, which filter waste from the blood. If either or both serum creatinine or GFR are abnormal, then your doctor will ask you to see a kidney specialist (a nephrologist).

The correlation between obesity and CKD was demonstrated in a large study of adults in Sweden which revealed that being overweight (BMI above 25) at age 20 was associated with a three-fold excess risk for CKD, in comparison with a BMI below 25. BMI above 30 among men and BMI above 35 among women any time during their lifetime were linked to three- to four-fold increases in CKD risk.

BMI is not the only marker for obesity, as some people have central obesity (the body shape described as an “apple,” in contrast to that of a “pear,” referring to where on the body more fat is located) without a BMI above 30, which is also a risk for metabolic complications.

A study completed in the Netherlands found that a higher waist-to-hip ratio was associated with lower GFR, lower effective kidney blood flow and higher filtration demand by the kidney, even after adjustments for sex, age, blood pressure and BMI.

The importance of performing the screening blood test in people at risk for CKD is that you may feel fine in the early stages and don’t develop any symptoms until the CKD is advanced, even possibly at the stage where dialysis or organ transplantation is needed. The goal is to identify kidney disease early when there may still be a possibility for either reversing the process or at least slowing the progression to kidney failure. In the case of obesity, the goal would be to proceed with weight loss followed by weight maintenance.


Problems breathing (i.e., “shortness of breath”), fatigue, leg swelling and limited ability to exercise are often attributed merely to obesity, however these symptoms need to be evaluated to determine if the heart could be the cause, especially if one or more of these symptoms change between doctor visits.

Typically the physician is focused on looking for evidence of atherosclerosis [ath-er-ō-skler-ōsis] (accumulation of fatty material in the blood vessels), which causes blockages in the arteries of the heart, leading to heart attacks and failure of the heart to pump as well as it should. However, in the presence of obesity, physicians often find heart failure without significant atherosclerosis or evidence of prior heart attacks. This is thought to be due to the stress of the excess weight on the vascular system, atherosclerosis of the small vessels, and the inflammation that comes from fat tissue that causes chemical changes, adding to vessel blockages.

This type of heart failure is diagnosed by an ultrasound of the heart (echocardiogram) and is referred to as “heart failure with preserved HFpEF” as compared to ‘‘heart failure with reduced ejection fraction,” or HFrEF. Patients with HFpEF tend to have fewer symptoms than those with HFrEF, suggesting that evaluation for possible heart failure should be done early rather than after many years of complaints. Although the treatment is the same for both types of heart failure, the goal of early diagnosis would be to slow or stop the progression of the heart failure to prevent the development of HFrEF. In this circumstance, the primary treatment will be weight loss and weight maintenance combined with regular physical activity.


Symptoms of neuropathy [nu-rop-a-the] (nerve damage) can include numbness, tingling, or pain in the arms and legs. Evaluation of such symptoms should always include evaluation for problems in the spine. However, obesity has been found to be associated with neuropathy in both the arms (as an example, the wrist) and the legs.

The Utah Diabetic Neuropathy Study (UDNS), published in 2013, examined 218 individuals with diabetes mellitus type 2 (the diabetes that results from insulin in the body not working as well as it should, plus decreasing production of insulin by the body) without neuropathy symptoms, or with symptoms present less than five years, in order to evaluate risk factors for neuropathy development. The study found that obesity and triglycerides [trī-glisĕr-īds] (sugar fats) were linked to the loss of small nerves associated with sensation in contrast to higher blood sugars, which were more likely to be linked to loss of nerve function of larger nerves such as those associated with motor function or movement. These findings suggest obesity and hypertriglyceridemia [hī-per-trī-glis'er-i-dē-mē-a] (elevated concentrations of triglycerides in the blood) significantly increase the risk for neuropathy, separate from blood sugar control.

In a separate study of 676 patients with carpal tunnel syndrome (“pinched nerve” in the wrist that causes numbness and tingling in the fingers) who were referred for nerve testing studies to confirm this suspected diagnosis, obesity was associated with an increased risk of developing this very common nerve damage. The risk of developing the damage averaged nine percent (a range of five to 13 percent) for each increase in BMI in patients 60 years and older.


Studies of lung function in obese adults have demonstrated decreased lung volume and capacity, as compared to healthy individuals.

When a patient presents with complaints of problems breathing, it is important that a full medical evaluation first be performed to determine if it is due to a lung- or heart-related problem. The evaluation of asthma in an overweight/obese person should include tests of lung function and assessment for allergic causes. These assessments may include the following lung function markers: forced vital capacity [FVC], forced expiratory volume in one second [FEV1], FEV1/FVC ratio, and forced expiratory flow – a measure of how much you can breathe out in one second--at 25 to 75 percent. The markers are typically measured by having you breathe into a long tube attached to a machine that automatically measures the amount and quickness of air inhaled and exhaled.

One study evaluated 286 patients with asthma in a real-life setting, including 96 who were overweight (33.6 percent of the study group) and 45 who were obese (14.1 percent). Lung function was significantly reduced in the overweight and obese asthmatic individuals in comparison with normal weight persons. Overweight individuals had almost double the risk and obese individuals had triple the risk of having very abnormal lung expansion capacity in comparison with normal weight persons. Both overweight and obese individuals had a risk two times higher of having an abnormal breathing capacity, with a lower probability of allergy compared with normal-weight asthmatic patients.

Another important study showed that weight loss can make a significant improvement in breathing capacity. In this study that evaluated lung function in obese people before and after weight loss, at 12 months after weight loss surgery that resulted in weight loss the obese patients with asthma had improvements in lung reathing capacity, suggesting that weight loss allows the lungs to expand in obese individuals, as well as in obese individuals that have a lung disease—asthma.


Pain in the joints, especially the knees, hips and back, is more likely to be present if you are obese. This is due to the excess weight adding to stress on the joints, leading to increased wear and tear, which is officially called “degenerative joint disease.” While surgical procedures can improve the pain, the benefits and success of joint replacement, especially of the knee and hip, can be affected by weight.

In a study that included over 8,000 individuals who had undergone knee surgeries at a large U.S. medical center, costs related to the surgery were assessed as a function of the patients’ BMI prior to the operation, with BMIs ranging from 15 to 73. Patients’ hospital length of stay and the direct medical costs were lowest for those with BMI in the normal to overweight range. Increasing BMI was associated with significantly longer hospital stays and costs. Every five-point increase in study subjects’ BMI beyond 30 was associated with approximately $250 to $300 in higher hospitalization costs in primary total knee arthroplasty (knee joint replacement surgery) and $600 to $650 higher hospitalization costs in total knee arthroplasty. For this reason, surgeons often recommend weight loss prior to proceeding with a joint replacement surgery.


Obesity is also associated with an increased risk for the development of many malignancies (cancers), including colorectal cancer; esophageal adenocarcinoma (cancer of the esophagus); and cancers of the stomach, gallbladder, pancreas, liver, kidney, postmenopausal breast, uterus and thyroid, as well as non-Hodgkin lymphoma, multiple myeloma (cancer of the plasma cells, a type of white blood cell present in the bone marrow) and prostate cancer...and this list continues to grow.

In addition to an association with greater incidence of cancer, overweight and obesity increase the risk of death with most of the malignancies noted above, as well as for those with premenopausal breast cancer and squamous cell mouth and tongue cancer. In the United States, the effects of overweight and obesity have been estimated to contribute to 14 percent of cancer deaths in men and 20 percent of cancer deaths in women. The presence of obesity also makes it more difficult to determine the correct doses of chemotherapy, leading to decreased treatment effectiveness. Maintaining a BMI below 25 has been projected to help prevent as many as 90,000 cancer deaths per year in the United States.

But can intentional weight loss protect you from the development of cancer? The Swedish Obese Subjects (SOS) study suggests so. The study examined over 4,000 obese individuals, half of whom underwent bariatric (weight-loss) surgery, compared to half without this surgery and studied what happened to their health over an average of 10 years. Those that had had the bariatric surgery and had lost weight showed a 40 percent reduction in developing cancer. In another study looking at the results of over 7,000 very obese individuals who had undergone gastric bypass surgery compared to over 7,000 who had not had the surgery, after seven years there was a 60 percent decrease in cancer death in those who underwent the weight loss surgery. These data suggest that intentional weight loss can have a significant impact on both cancer incidence and death.


The complications related to obesity may start as early as when the BMI just barely meets current criteria for obesity (currently a BMI of 30), and not when above 35 or 40 as we are often led to believe from what we see in media stories.

While maintaining a healthy lifestyle is of the utmost importance, any amount of weight loss, even 15 to 20 pounds if kept off, can have a significant positive effect on your long-term health. Set a short-term goal that should be realistic, such as losing 10 pounds in three months. This can be re-evaluated at the end of the three months with a new goal set for the next three months.

Dr. Kathleen l. Wyne is an endocrinologist in Houston where she sees patients for management of all components of metabolic syndrome and is active in clinical research. She is currently coordinating a large community-based diabetes prevention project in an underserved urban Mexican-American community with a focus on developing strategies to facilitate weight loss in young, adult Latino women. Her research team is also studying factors that impact the progression of fatty liver disease. Dr. Wyne earned her MD and PhD at the University of Chicago