Complex Underlying Causes of Obesity

Q:  I am concerned about my sister's health and wonder if you might have some suggestions. My sister, age 38, has always been somewhat heavy, but since she had thyroid surgery about seven years ago, her weight has increased considerably. She is 5'3" and I would guess that she weighs from 200 to 250 pounds. What perplexes me is that she seems to eat less than I do; yet I am of normal weight. I have spent holidays and family vacations with her, and it seems impossible that her eating habits would enable her to maintain her weight.

My knowledge of her medical history is sketchy, at best. After she had a non-cancerous growth removed from her thyroid several years ago, she was placed on steroids. She then gained a great deal of weight. She also has excessive facial hair that predates the thyroid surgery. She has undergone various medical testing and seems to have given up on finding any help losing weight.

She has made comments about having to accept herself as she is, and that her family needs to do the same. But, with another sister who is diabetic and has a family history of heart disease, I find her weight unacceptable. I feel that if she had cancer or some other health-threatening problem, I would have an obligation to insist that she get medical attention, and I feel that this is a similarly serious problem.

As I'm sure you know, obesity is a tricky topic. I fear that the doctors who see her assume that she is "to blame" for her weight problems. I would be very grateful for any suggestions you might have.

A:  There is no question that obesity poses a major risk to health. Instead of going just by weight, we use the Body Mass Index (BMI) which is weight in kg divided by height in meters squared. You can also calculate your BMI multiplying your weight in pounds by 700. Then divide the result by your height in inches; then divide by your height in inches again. By my chart, if your sister weighs 225, her BMI is 40. The threshold for being "overweight" is about 150 pounds and at 170 she becomes "obese." Overweight is defined as BMI of 25-29, and 30 and over qualifies as "obesity." Over 32 is considered "morbidly obese" and in danger of serious health problems.

Obese people are at greater risk for high blood pressure, high cholesterol, diabetes, coronary heart disease, stroke, sleep apnea, gallbladder disease, liver disease, arthritis, and even cancer (colon, uterine, and breast). In the Nurses' Health Study, women who gained more than 20 pounds from age 18 to midlife, DOUBLED their risk for breast cancer.

Weight is probably about 25% determined by heredity, 25% by environment (other medical conditions, diet, exercise, etc), and 50% by a combination of both. Your sister is mostly likely eating LESS calories than you, but she started out "somewhat heavy" and then her obesity has been worsened by medical problems. The thyroid is so intimately tied to metabolism that it is common to have weight fluctuations when the thyroid is under- or over-active or with surgical removal. It can be very hard to "bounce back" to one's usual weight afterwards. Steroids can also cause weight gain. The excess facial hair could indicate other underlying problems with polycystic ovary syndrome or her adrenal glands.

Prevention is the best cure when it comes to obesity because it is very difficult to treat. That's why we have a billion dollar weight loss industry in the US. Your sister is right -- she needs the understanding and support of her family. You're right too -- she needs to see an endocrinologist or could start with a good primary care physician. She may later need to work with a dietitian, a counselor, a personal trainer, and support groups.

Most of all she needs to choose to get help; you can't force her to do.

"Dear Doctor" is a compilation of patient questions answered by doctors from the Medical College of Wisconsin.