Obesity linked to premature death

It is well known that being overweight can lead to health complications including diabetes, heart disease, stroke and cancer.

A recent study published in Lancet reports on a meta-analysis of 239 prospective studies published from 1970 to last year (median follow-up 13·7 years).  Of those 3 951 455 people in 189 studies were never-smokers without chronic diseases at recruitment who survived 5 years, of whom 385 879 died.   The investigators extracted their information from 10 625 411 participants in Asia, Australia and New Zealand, Europe, and North America.

They compared the risk of death to people's body mass index, or BMI, a measure of body fat that is calculated using height and weight.  They defined a BMI from 18.5 to 25 as normal, 25-30 as overweight, 30-35 as moderately obese and over 40 as severely obese.

In the study, the risk of dying before the age of 70 was 19 percent for men and 11 percent for women of normal weight.

But that risk jumped to 30 percent and 15 percent, respectively, for obese men and women.  The investigators found that overweight people die one year earlier than expected and that moderately obese people die up to three years prematurely.

The World Health Organization estimates that 1.3 billion adults worldwide are overweight, and 600 million more are obese. The associations of both overweight and obesity with higher all-cause mortality were broadly consistent in all four continents. As common diseases such as heart disease, stroke, diabetes and cancer have been strongly associated to obesity, strategies to combat it are needed all around the globe.

Worldwide increase in obesity

A study that was published in Lancet reports an alarming worldwide increase in the prevalence of obesity.

The authors estimated incidence and trends in mean body-mass index (BMI) categories, of males and females in 186 countries.

The researchers gathered population-based data that measured the height and weight of 19 million adults (9·9 million men and 9·3 million women) for which estimates were made.  They used statistical methods to estimate trends in global and national weight patterns from 1975 to 2014.  During this period global age-standardized mean BMI increased from 21·7 kg/m² to 24.2 kg/m² in in men, and from 22·1 kg/m² in to 24·4 kg/m² in women (normal BMI range is 18.5 to 22.1 kg/m²⁾. Regional mean BMIs in 2014 for men ranged from 25 kg/m² in central Africa and south Asia to 29.2 kg/m² in Polynesia and Micronesia; for women the range was from 21.8 kg/m² in south Asia to 32.2 kg/m² in Polynesia and Micronesia (BMI for the overweight category ranges from 25 kg/m² to 30 kg/m², for the obese from 30 kg/m² to 35 kg/m² while those individuals having a BMI over 35 are morbidly obese).  Finally 2.3% of the world's men and 5·0% of women were morbidly obese (i.e., have BMI ≥35 kg/m²).

Over the past 40 years there has been an unprecedented increase in the number of obese adults worldwide, climbing to about 640 million from 105 million in 1975.  If the post-2000 trends continue, by 2025, global obesity prevalence will reach 18% in men and surpass 21% in women; severe obesity will surpass 6% in men and 9% in women.  The study found that the number of obese people surpasses the number of people who are underweight.

Cancers linked to Obesity

Obesity is a major contributor to the development of cancer.  According to the National Cancer Institute obesity is associated with increased risks for cancer of the esophagus, pancreas, colon and rectum, breast (after menopause), endometrium, kidney, thyroid, and gallbladder.

 

NHANES 2007-2008 survey found 68 percent of the U.S. adults age 20 years and older are overweight or obese and 17 percent of children and teens ages 2 to 19, are obese.  According to NCI Surveillance, Epidemiology, and End Results (SEER) data, it is estimated that in 2007 in the United States, about 34,000 new cases of cancer in men (4 percent) and 50,500 in women (7 percent) were due to obesity.

In 2003, Calle et al published in NEJM the results of a study of more than 900,000 healthy adults that were followed for 16 years.  The study authors concluded that excess fat could account for 14% of all deaths from cancer in men and 20% of those in women.

A recent study of 92,834 British women enrolled in a database for cancer screening, Fourkala et al reported in an article published in BMJ Open that women who go up a skirt size every decade between their 20s and their 60s are at increased risk of postmenopausal breast cancer.  They also found that “an increase of one size every 10 years led to a 33 percent rise in the risk of postmenopausal breast cancer, while an increase of two sizes per decade led to a 77 percent rise in risk.

Bhaskaran et al study of 5.2 million adults that was published in Lancet found that 166 955 individuals developed cancer and that body-mass index (BMI) was associated with 17 of 22 cancers.  Although the effects varied substantially by site, increase in BMI was roughly linearly associated with cancers of the uterus, gallbladder, kidney, cervix, and leukemia.  BMI increase was positively associated with liver, colon, ovarian, and postmenopausal breast cancers overall. They estimated inverse associations with prostate and premenopausal breast cancer risk, both overall and in non-smokers. By contrast, for lung and oral cavity cancer, they observed no association in non-smokers.  Assuming causality, 41% of uterine and 10% or more of gallbladder, kidney, liver, and colon cancers could be attributable to excess weight. They conclude that extra weight could contribute to more than 12,000 cases of cancer in the UK population every year.

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