Fewer than 12.2% of the US adult population is metabolically healthy, using NHANES data from 2009 to 2016. That is roughly one adult in eight. It is the single most useful number for understanding why individual advice keeps failing.
Obesity is a symptom, not the root cause
It is wrongly assumed that excessive caloric intake is the root cause of obesity. A calorie of food energy has different metabolic fates depending on the hormonal environment it arrives in. The same calorie may be burned or stored depending on insulin, and insulin depends on what the calorie was made of.
Weight depends on many factors, but the mechanism most often left out is insulin’s role in fat storage. Address that and the arithmetic changes; ignore it and the arithmetic does not work in practice however sound it looks on paper.
The odds under standard advice
The standard instruction from dietitians and physicians is to eat less and move more. It does not produce favourable odds for losing weight and keeping it off. That is an empirical observation about outcomes, not a criticism of effort.
Evidence from multiple randomised controlled trials indicates that a higher-fat, lower-carbohydrate diet outperforms a low-fat diet for both weight loss and cardiovascular risk reduction.
Why each attempt gets harder
Weight regained after loss frequently exceeds what was lost, and each subsequent attempt becomes more difficult. The mechanism has a name — relapse-induced hyperplasia of adipose tissue, colloquially rubber-banding or the fat yo-yo. Repeated cycles increase the number of fat cells available for storage, which is not reversed by the next diet.
Smoking or obesity: which carries the higher hazard ratio?
A hazard ratio compares hazard rates between conditions. Put in context, the comparison between smoking and obesity is closer than most people expect, and for several outcomes obesity does not come out favourably. It is a useful corrective for anyone who regards obesity as a cosmetic matter and smoking as a medical one.
A generational and national problem
Blue Cross Blue Shield’s study of millennial health found a rapid decline in health index score after a certain age, with metabolic conditions prominent. Obesity is also the leading medical reason applicants fail to qualify for US military service — 27% of young people aged 17 to 24 are too obese to serve.
Globally, chronic non-communicable disease accounts for the majority of the disease burden, most of it diet-associated. The dual burden is real: hunger persists in some populations while excess kills in others, and both are malnutrition.
Sedentary time is its own variable
On average, every hour of television viewed after age 25 reduces life expectancy by an estimated 21.8 minutes. (Br J Sports Med. 2012 Oct;46(13):927-30.) Inactivity is not merely an absence of exercise; sustained sedentary time has independent metabolic consequences.
The epidemic framing
Reversing obesity, prediabetes and type 2 diabetes is the most important public health challenge of the present moment. When every species in an environment develops the same disease, the question of whether to call it an epidemic or a pandemic matters less than the observation that the environment is the exposure.
