We've been hearing it since we were kids: Don't judge a book by its cover. It's true for books and it's even truer for our patients and clients. It can be difficult to keep an open mind when we see someone whose appearance can easily be associated with overeating and being sedentary and whom we might assume is a textbook case of metabolic syndrome even before we've seen their blood work.

However like it so often does the data can surprise us. There are overweight and obese people who have metabolic profiles we would consider healthy often referred to as the metabolically healthy obese. Even more common than this however are people who are what is casually known as skinny-fat or TOFI: thin outside fat inside. That is they have a normal body weight but have metabolic profiles which we typically associate with obesity and metabolic syndrome known as the normal weight obese.

Based on body mass index (BMI) alone the normal weight obese may be classified as having a healthy body weight. However when the more clinically relevant body composition is taken into account these people are shown to have unhealthy proportions of body fat compared to lean mass and may also have comparatively more of their fat stored in metabolically damaging visceral deposits as opposed to subcutaneously including in the liver as is seen with increasing recognition of non-alcoholic fatty liver disease in people of normal weight.

For reasons of genetics or maybe just plain luck some people seem to be protected against excess body fat accumulation. But just because these people remain lean and their outward appearances reflect our modern Western aesthetic ideals doesn't mean unhealthy diets and lifestyles aren't wreaking havoc on them internally. In the clinical setting these patients and clients might present with an array of both subjective and directly measurable signs of carbohydrate intolerance inflammation and dyslipidemia. The numbers don't lie: the lab work can give us a wealth of information that is not reflected in the mirror.

These signs might include some of the hallmarks of metabolic syndrome minus the excess body fat and abdominal obesity: elevations in fasting blood glucose hemoglobin A1c triglycerides C-reactive protein and small dense LDL particles; decreased HDL; and hypertension. Subjectively as reported by the patients symptoms might include several things linked to poor blood glucose control such as energy crashes brain fog mood swings irritability and signs of hypoglycemia when meals are skipped or delayed. 

Research indicates that many more otherwise idiopathic health concerns might be related to poor diet in the normal weight obese ranging from acne to poor eyesight and even to male pattern baldness. Studies looking at heart failure have shown that the normal weight obese (with metabolic syndrome) are at much greater risk than the metabolically healthy obese. In fact while BMI itself had no association with heart failure risk overweight and obese subjects without metabolic syndrome had the lowest 6-year risk compared to normal weight individuals with metabolic syndrome. Post-menopausal women with normal weight obesity show increased oxidative stress compared to those who are obese but metabolically healthy.

Furthermore because of the influence of insulin on aromatase and therefore levels of estrogen and testosterone insulin resistance in the normal weight obese should be considered as an underlying factor in hormonally-driven conditions such as polycystic ovarian syndrome (PCOS) benign uterine and prostatic hyperplasia and gynecomastia. Attempting to correct these hormonal imbalances without identifying and addressing their primary cause is like bailing water out of a leaky boat without first stopping to patch the hole; that is to say you merely manage the symptoms while the true problem continues wreaking havoc.

That such a diverse group of clinical presentations can be tied to the hyperinsulinemia and inflammation likely induced by a carbohydrate- and grain-heavy diet low in total fat and/or high in the wrong types of fat shows us that excess body fat is only one result of the misguided conventional dietary recommendations of the last half-century. People who sidestep the fate of gaining weight are not immune to the myriad other effects of a poor diet upon their health and in fact a lack of visible proof of these effects might make it more difficult to help these patients see the connection between their dietary choices and suboptimal health.

Thus we find some truth in the old saying: beauty is only skin deep.