Being overweight or obese raises the likelihood of renal failure, ESRD, stones, and cancer.
America’s obesity epidemic continues unabated and has spread to other places where the Western diet prevails. Every new health survey shows that heaviness and obesity continue to rise, especially in children and younger adults. Besides multiplying the risk of cardiovascular disease and diabetes, newer research shows that obesity also heightens the risk of chronic renal failure (CRF), end-stage renal disease (ESRD), kidney stones, and renal cell carcinoma (RCC).
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CRF
Elisabeth Ejerblad, MD, of the Karolinska Institute in Stockholm, Sweden, and her colleagues reported earlier this year that being overweight (BMI over 25 kg/m2) at age 20 was associated with a threefold excess risk for CRF (J Am Soc Nephrol. 2006:17:1695-1702). Obesity (BMI over 30 kg/m2) among men and morbid obesity (BMI over 35 kg/m2) among women at any point in life was linked to a three- to fourfold increased risk. Although the strongest association was with diabetic nephropathy, analyses confined to persons without diabetes or hypertension still revealed that subjects who were overweight at age 20 had a threefold higher risk. Diabetic nephropathy was the most likely subtype of CRF associated with heaviness and obesity.
ESRD
A team led by Chi-yuan Hsu, MD, MSc, of the University of California, San Francisco, found that higher BMI was a risk factor for ESRD in Kaiser Permamente members between 1964 and 1985 (Ann Intern Med. 2006:144:21-28). Compared with persons of normal weight (BMI 18.5-
24.9 kg/m2), those who were overweight (BMI 25-29.9 kg/m2) had a nearly two times higher risk of ESRD. Subjects with class I and II obesity (BMI of 30-34.9 and 35-39.9 kg/m2, respectively) were at nearly fourfold and sixfold higher risk. Extreme obesity (40 kg/m2 or higher) was associated with a sevenfold greater risk. Higher BMI was more strongly associated with ESRD in participants younger than 40 years who were obese at first measurement.
Kidney stones
Eric N. Taylor, MD, of the Channing Laboratory in Boston, and his colleagues reported last year that several measures of excessive adiposity were linked to kidney stones (JAMA. 2005; 293:455-462). The findings were based on data from the Health Professionals Follow-up Study and the Nurses’ Health Study I (which enrolled women between the ages of 30 and 55 years)
and Nurses’ Health Study II (which enrolled women between the ages of 25 and 42 years). The researchers documented 4,827 incident kidney stones over a combined 46 years of follow-
up. Stones were 44% more likely to develop in men who weighed more than 220 pounds than
in men who weighed less than 150 pounds, after adjusting for age, dietary factors, fluid intake, and thiazide use. In both nurses’ studies, women who weighed more than 220 pounds were almost twice as likely to develop stones compared with women who weighed less than
150 pounds.
In addition, a BMI of 30 kg/m2 or greater was associated with a 33% increased risk of kidney stones in men and a twofold higher risk in women. A waist circumference greater than 43 cm in
men was associated with a 48% increased risk of kidney stones compared with men with a waist circumference less than 34 cm. A waist circumference greater than 40 cm in women was associated with a nearly twofold increased risk compared with women with a waist circumference less than 31 cm. Any weight gain over five pounds in men or 20 pounds in women entailed increased risk.
RCC
Two recent studies have strengthened evidence linking obesity to RCC. In the European Prospective Investigation into Cancer and Nutrition, Tobias Pischon, MD, of the German Institute of Human Nutrition in Nuthetal, and his colleagues found that, compared with women in the lowest quintile of body weight, BMI, and waist and hip circumference, those in the highest quintile of these measurements were at approximately two times higher risk of RCC (Int J Cancer. 2006;118:728-738). After controlling for body weight, however, waist and hip circumference were no longer significant.
Among men, no obesity measure increased RCC risk. In fact, after accounting for body weight,
an increase in hip circumference was associated with a decrease in RCC risk. Men in the high-
est quintile of hip circumference (106 cm or more) were at 56% lower risk of RCC compared with those in the lowest quintile (less than 95.5 cm). The finding suggests that “in men, the fat distribution pattern, and particularly hip circumference, may be more predictive of RCC that obesity per se,” the authors noted.
A similar study by a team of Swedish investigators (Cancer Causes & Control. 2006;17:901-909) found that compared with men of normal weight, obese men had a nearly twofold increased risk of RCC as well as other cancers. Compared with men whose weight remained stable over six years of follow-up, men with more than a 15% increase had an elevated risk of renal cancers.
