In a recent public spat, New Jersey Governor Chris Christie told former White House physician Connie Mariano to "shut up" about his weight when she expressed concern that he might die in office if he were elected president. Christie openly acknowledges that he struggles with his weight but claimed that he is "remarkably healthy."

Christie might be right, but if so, he would be a medical miracle. The governor said that unless Mariano gave him a physical exam or learned his family history, she could make no judgment about his health. He is wrong, because any casual observer can see that Christie is obese, as he would himself admit, and the reality is that obesity is known to lead to an increased risk for premature death. Most Americans die sooner than necessary by stroke, heart attack or cancer, and obesity increases the risk for all of these. Christie should remember that the Titanic was a healthy ship just before hitting the iceberg.

Yes, in rare circumstances we can point to a few obese individuals who do not appear to be at increased risk for heart disease; few things are absolute with biology. But that should offer no consolation to Christie or anyone else carrying excess weight. Just because a neighbor won the lottery does not mean you will.

We know absolutely that obesity creates an increased risk of diabetes. (The data below are from publicly available government sources, summarized and cited in Calorie Wars: Fat, Fact and Fiction). In 1990 about 11 million Americans had type-2 (adult onset) diabetes, a disease of insulin resistance that commonly coexists with obesity. Just nine years later the number was 16 million, or about 6 percent of all Americans. Then, from 1999 to 2003, we saw a 41-percent increase in diagnosed diabetes. Since then obesity has ballooned to an astounding 64 percent of all Americans, and the number of diabetics continues to explode. Note too that the insulin resistance syndrome associated with obesity has other dire consequences, including hypertension and the increased risk of atherosclerotic cardiovascular disease.

Another problem with "fat but fit" is simple mechanics. The human body evolved from a period of deprivation where food was scarce and difficult to obtain. Our ancestors were almost certainly lean. In any case, we are not engineered to bear excess weight on our joints. Obesity leads to arthritis and can lead one down the path to knee replacement, not only because of the mechanical stress it can cause but because fat produces chemicals that attack cartilage. Think of it this way: If you stuff 20 people into a Volkswagon Bug, the suspension will wear out faster and the engine will have to work harder, ultimately reducing its useful life.

If you still believe fat can be fit, consider the following realities:

• About 400,000 deaths per year are attributed to obesity; individuals with a body mass index (BMI) over 30 have a 50-percent to 100-percent increased risk of premature death from all causes compared with lean people with lower BMIs.
• High blood pressure is twice as common in obese adults than in those with a healthy weight; obesity is associated with elevated blood fat (triglycerides) and decreased good cholesterol (HDL).
• A weight gain of only 11 to 18 pounds increases the risk of developing type-2 diabetes; over 80 percent of people with type-2 diabetes are overweight or obese.
• Obesity is associated with an increased risk of cancer of the uterus, colon, gall bladder, prostate and kidney, and with postmenopausal breast cancer.
• Sleep apnea is more common in obese people, and some recent studies have indicated that a lack of sleep might affect hormone levels to a degree that could indeed cause weight gain.
• Obesity during pregnancy is associated with a greater risk of birth defects, including spina bifida.
• Every increase in weight of two pounds increases the risk of arthritis by 9 percent to 13 percent.

We can see why Christie's claim to be "remarkably healthy" should be greeted with some skepticism.

One final consideration on the idea of being fat but fit: Obesity can affect quality of life through limited mobility, decreased physical endurance and social stigmatization. While we know we should not judge a book by its cover, most of us do, at least to some extent. Yes, you should be comfortable with and love yourself for who you are, and you need not look like a fashion model. But that truth is no excuse for adopting the dangerous myth that fat can be fit.