The possible relationship between diet and mortality remains an important area of investigation. Previous studies have identified dietary factors associated with mortality. Those found to correlate with reduced mortality include nuts,^1-4 fruit,^5,6 cereal fiber,² polyunsaturated fatty acids (PUFAs),² ω-3PUFAs,³ green salad,⁷ Mediterranean dietary patterns,^8-11 “healthy” or “prudent” dietary patterns,^10,12,13 plant-based diet scores,¹⁴ plant-based low-carbohydrate diets,¹⁵ and vegetarian diets.^4,16,17 Associations with increased mortality have been found for a high glycemic load,² meat,^6,7 red meat,^18,19 processed meat,^18,19 eggs,⁷ potatoes,⁵ increased energy intake,²⁰ and animal-based low-carbohydrate diets.¹⁵

The prevalence of class III obesity (body mass index [BMI]≥40 kg/m²) has increased dramatically in several countries and currently affects 6% of adults in the US, with uncertain impact on the risks of illness and death. Using data from a large pooled study, we evaluated the risk of death, overall and due to a wide range of causes, and years of life expectancy lost associated with class III obesity. In a pooled analysis of 20 prospective studies from the United States, Sweden, and Australia, we estimated sex- and age-adjusted total and cause-specific mortality rates (deaths per 100,000 persons per year) and multivariable-adjusted hazard ratios for adults, aged 19–83 y at baseline, classified as obese class III (BMI 40.0–59.9 kg/m²) compared with those classified as normal weight (BMI 18.5–24.9 kg/m²). Participants reporting ever smoking cigarettes or a history of chronic disease (heart disease, cancer, stroke, or emphysema) on baseline questionnaires were excluded. Among 9,564 class III obesity participants, mortality rates were 856.0 in men and 663.0 in women during the study period (1976–2009). Among 304,011 normal-weight participants, rates were 346.7 and 280.5 in men and women, respectively. Deaths from heart disease contributed largely to the excess rates in the class III obesity group (rate differences = 238.9 and 132.8 in men and women, respectively), followed by deaths from cancer (rate differences = 36.7 and 62.3 in men and women, respectively) and diabetes (rate differences = 51.2 and 29.2 in men and women, respectively). Within the class III obesity range, multivariable-adjusted hazard ratios for total deaths and deaths due to heart disease, cancer, diabetes, nephritis/nephrotic syndrome/nephrosis, chronic lower respiratory disease, and influenza/pneumonia increased with increasing BMI. Compared with normal-weight BMI, a BMI of 40–44.9, 45–49.9, 50–54.9, and 55–59.9 kg/m² was associated with an estimated 6.5 (95% CI: 5.7–7.3), 8.9 (95% CI: 7.4–10.4), 9.8 (95% CI: 7.4–12.2), and 13.7 (95% CI: 10.5–16.9) y of life lost. A limitation was that BMI was mainly ascertained by self-report. Class III obesity is associated with substantially elevated rates of total mortality, with most of the excess deaths due to heart disease, cancer, and diabetes, and major reductions in life expectancy compared with normal weight. Please see later in the article for the Editors' Summary The number of obese people (individuals with an excessive amount of body fat) is increasing rapidly in many countries. Worldwide, according to the Global Burden of Disease Study 2013, more than a third of all adults are now overweight or obese. Obesity is defined as having a body mass index (BMI, an indicator of body fat calculated by dividing a person's weight in kilograms by their height in meters squared) of more than 30 kg/m² (a 183-cm [6-ft] tall man who weighs more than 100 kg [221 lbs] is obese). Compared to people with a healthy weight (a BMI between 18.5 and 24.9 kg/m²), overweight and obese individuals (who have a BMI between 25.0 and 29.9 kg/m² and a BMI of 30 kg/m² or more, respectively) have an increased risk of developing diabetes, heart disease, stroke, and some cancers, and tend to die younger. Because people become unhealthily fat by consuming food and drink that contains more energy (kilocalories) than they need for their daily activities, obesity can be prevented or treated by eating less food and by increasing physical activity. Class III obesity (extreme, or morbid, obesity), which is defined as a BMI of more than 40 kg/m², is emerging as a major public health problem in several high-income countries. In the US, for example, 6% of adults are now morbidly obese. Because extreme obesity used to be relatively uncommon, little is known about the burden of disease, including total and cause-specific mortality (death) rates, among individuals with class III obesity. Before we can prevent and treat class III obesity effectively, we need a better understanding of the health risks associated with this condition. In this pooled analysis of prospective cohort studies, the researchers evaluate the risk of total and cause-specific death and the years of life lost associated with class III obesity. A pooled analysis analyzes the data from several studies as if the data came from one large study; prospective cohort studies record the characteristics of a group of participants at baseline and follow them to see which individuals develop a specific condition. The researchers included 20 prospective (mainly US) cohort studies from the National Cancer Institute Cohort Consortium (a partnership that studies cancer by undertaking large-scale collaborations) in their pooled analysis. After excluding individuals who had ever smoked and people with a history of chronic disease, the analysis included 9,564 adults who were classified as class III obese based on self-reported height and weight at baseline and 304,011 normal-weight adults. Among the participants with class III obesity, mortality rates (deaths per 100,000 persons per year) during the 30-year study period were 856.0 and 663.0 in men and women, respectively, whereas the mortality rates among normal-weight men and women were 346.7 and 280.5, respectively. Heart disease was the major contributor to the excess death rate among individuals with class III obesity, followed by cancer and diabetes. Statistical analyses of the pooled data indicate that the risk of all-cause death and death due to heart disease, cancer, diabetes, and several other diseases increased with increasing BMI. Finally, compared with having a normal weight, having a BMI between 40 and 59 kg/m² resulted in an estimated loss of 6.5 to 13.7 years of life. These findings indicate that class III obesity is associated with a substantially increased rate of death. Notably, this death rate increase is similar to the increase associated with smoking among normal-weight people. The findings also suggest that heart disease, cancer, and diabetes are responsible for most of the excess deaths among people with class III obesity and that having class III obesity results in major reductions in life expectancy. Importantly, the number of years of life lost continues to increase for BMI values above 50 kg/m², and beyond this point, the loss of life expectancy exceeds that associated with smoking among normal-weight people. The accuracy of these findings is limited by the use of self-reported height and weight measurements to calculate BMI and by the use of BMI as the sole measure of obesity. Moreover, these findings may not be generalizable to all populations. Nevertheless, these findings highlight the need to develop more effective interventions to combat the growing public health problem of class III obesity. Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001673.

Colorectal cancer remains the second leading cause of cancer mortality in the United States.¹ Although much attention has focused on improving screening for and treatment of colorectal cancer, enhancing primary prevention through risk factor reduction remains an important objective.

In a 6-year prospective study, the authors examined the relation between diet and incident colon cancer among 32, 051 non-Hispanic white cohort members of the Adventist Health Study (California, 1976–1982) who, at baseline, had no documented or reported history of cancer. The risk of colon cancer was determined from proportional hazards regression with adjustment for age and other covariates. The authors found a positive association with total meat intake (risk ratio (RR) for ≥1 time/week vs. no meat intake = 1.85, 95% confidence interval (Cl) 1.19–2.87; p for trend = 0.01) and, among subjects who favored specific types of meat, positive associations with red meat intake (RR for ≥ 1 time/week vs. no red meat intake = 1.90, 95% Cl 1.16–3.11; p for trend = 0.02) and white meat intake (RR for ≥1 time/week vs. no white meat intake = 3.29, 95% CI 1.60–6.75; p for trend = 0.006). An inverse association with legume intake (RR for ≥2 times/week vs. 25.6 kg/m2) vs. tertile I (<22.5 kg/m2) = 2.63, 95% Cl 1.12–6.13; p for trend = 0.05). A complex relation was identified whereby subjects exhibiting a high red meat intake, a low legume intake, and a high body mass experienced a more than threefold elevation in risk relative to all other patterns based on these variables. This pattern of putative risk factors would likely contribute to increases in both insulin resistance (high body mass, high red meat intake) and glycemic load (low legume intake), a synergism that, if causal, implicates hyperinsulinemic exposure in colon carcinogenesis. The overall findings from this cohort identify both red meat intake and white meat intake as important dietary risk factors for colon cancer and raise the possibility that the risk due to red meat intake reflects a more complex etiology. Am J Epidemiol 1998; 148: 761–74.

The waterpipe, also known as shisha, hookah, narghile, goza, and hubble bubble, has long been used for tobacco consumption in the Middle East, India, and parts of Asia, and more recently has been introduced into the smokeless tobacco market in western nations. We reviewed the published literature on waterpipe use to estimate daily nicotine exposure among adult waterpipe smokers. We identified six recent studies that measured the nicotine or cotinine levels associated with waterpipe smoking in four countries (Lebanon, Jordan, Kuwait, and India). Four of these studies directly measured nicotine or cotinine levels in human subjects. The remaining two studies used smoking machines to measure the nicotine yield in smoking condensate produced by the waterpipe. Meta-analysis of the human data indicated that daily use of the waterpipe produced a 24-hr urinary cotinine level of 0.785 μg/ml (95% CI=0.578–0.991 μg/ml), a nicotine absorption rate equivalent to smoking 10 cigarettes/day (95% CI=7–13 cigarettes/day). Even among subjects who were not daily waterpipe smokers, a single session of waterpipe use produced a urinary cotinine level that was equivalent to smoking two cigarettes in one day. Estimates of the nicotine produced by waterpipe use can vary because of burn temperature, type of tobacco, waterpipe design, individual smoking pattern, and duration of the waterpipe smoking habit. Our quantitative synthesis of the limited human data from four nations indicates that daily use of waterpipes produces nicotine absorption of a magnitude similar to that produced by daily cigarette use.

Aim: To examine the relation between meat intake and diabetes occurrence in adults. Methods: In a prospective cohort study we examined the relation between diet and incident diabetes recorded among 8,401 cohort members (ages 45–88 years) of the Adventist Mortality Study and Adventist Health Study (California, USA) who were non-diabetic at baseline. During the 17-year follow-up, we identified 543 incident diabetes cases. Results: (1) Subjects who were weekly consumers of all meats were 29% (OR = 1.29; 95% CI 1.08, 1.55) more likely (relative to zero meat intake) to develop diabetes. (2) Subjects who consumed any processed meats (salted fish and frankfurters) were 38% (OR = 1.38; 95% CI 1.05–1.82) more likely to develop diabetes. (3) Long-term adherence (over a 17-year interval) to a diet that included at least weekly meat intake was associated with a 74% increase (OR = 1.74; 95% CI 1.36–2.22) in odds of diabetes relative to long-term adherence to a vegetarian diet (zero meat intake). Further analyses indicated that some of this risk may be attributable to obesity and/or weight gain – both of which were strong risk factors in this cohort. It is noteworthy that even after control for weight and weight change, weekly meat intake remained an important risk factor (OR = 1.38; 95% CI 1.06–1.08) for diabetes. Conclusions: Our findings raise the possibility that meat intake, particularly processed meats, is a dietary risk factor for diabetes.