Читать книгу Textbook of Lifestyle Medicine - Labros S. Sidossis - Страница 59

Unhealthy weight is a well‐documented risk factor for NCDs development, even in the absence of other major risk factors. Maintaining a healthy weight and refraining from smoking increases the years spent in good health, in both men and women. For obese men, the number of years spent in good health are decreased by 4.6 years, relative to men living a healthy life. For men who smoke, the number of years spent in good health are decreased by 7.8 years. The respective decreases for women are 4.5 and 6.0 years, for obese and smokers, respectively.

FIGURE 3.3 Total annual number of deaths by risk factor.

Source: Reprinted with permission from the Global Burden of Disease Collaborative Network. Global Burden of Disease Study 2017. Institute for Health Metrics and Evaluation (IHME) (2018).

FIGURE 3.4 Map of the world showing estimated gains in life expectancy with elimination of physical inactivity.

Source: Reprinted with permission from Lee et al. (2012).

In addition, in a meta‐analysis of 230 cohort studies (207 publications), overweight and obesity were associated with increased risk of all‐cause mortality, with the lowest risk observed at BMI 23–24 kg/m² among never smokers, 22–23 kg/m² among healthy never smokers, and 20–22 kg/m² with longer durations of follow‐up.

As is usually the case, not all studies agree; data from the Dutch Burden of Disease study suggest that elimination of smoking or obesity does not result in absolute compression of morbidity but slightly increases the part of life lived in good health (which, by the way, is very important!).

Regarding the risk for developing T2DM, findings from the Uppsala Longitudinal Study of Adult Men (ULSAM) cohort indicated that after 20 years of follow‐up, those being overweight/obese but free of MetS had approximately 3.5 times increased risk of developing T2DM; the risk was eight times higher for overweight/obese individuals with MetS, relative to those of normal weight and free of MetS.

Contrary to the above findings suggesting that overweight/obesity is a risk factor for NCDs, other studies have shown that overweight and even grade 1 obesity (BMI = 30–35 kg/m²) are related to decreased all‐cause mortality by 6% and 5%, respectively, compared to those of normal BMI. Still, obesity grades 2 and 3 (BMI > 35 kg/m²) are associated with 18% and 29% increased risk of all‐cause mortality, respectively, compared to those of normal BMI.

There are many studies on BMI and mortality without uniform results. This is because many factors have been shown to confound the relationship between BMI and longevity. Possible residual confounding factors might be age, disease‐related weight loss, and individuals who smoked, had underlying diseases (e.g., cancer), or suffered early deaths.

In the elderly, mortality risk increases at BMIs lower than 22 kg/m², which is not seen in younger adults, while a lower risk is observed among those with overweight and mild obesity. This paradoxical finding, i.e., lower mortality at higher than “healthy” BMI levels, has been termed “the obesity paradox.” There are many possible mechanisms to explain these findings. Excess fat may act as a metabolic reserve during illness or injury. In addition, because of lower noradrenaline‐stimulated lipolytic activity in visceral fat as age increases (which leads to insulin resistance and morbidity), individuals may be less affected by excess adiposity. Moreover, physicians often prescribe more medications to those with overweight and obesity, which may indirectly contribute to the obesity paradox.

Frequent changes from normal to obese and back (yo‐yo effect) have been linked to more than twofold increased risk of all‐cause mortality, relative to stable normal BMI. However, changes from normal weight to overweight (not obesity) were not linked to elevated all‐cause mortality risk, compared to stable normal weight. These findings were similar for CVD‐ and cancer‐specific mortality.