A confusing fact is that, although we know that obesity can lead to increased risk of variety of negative health effects, such as diabetes and metabolic syndrome, there are people who are obese and yet seem to avoid these impacts. A new study published in the Annals of Internal Medicine suggests that such appearances may be deceiving especially with regard to kidney disease.
Dr. Yoosoo Chang from the Sungkyunkwan University School of Medicine in Seoul, South Korea, and colleagues, followed the health of over 62,000 healthy young and middle-aged men and women. On the basis of each person's Body Mass Index, they were described as:
- underweight (BMI of less than 18.5)
- normal weight (18.5 to 22.9)
- overweight (23 to 24.9)
- obese (25 kg/m2)
(Note: these are Asian-specific cutpoints.)
The participants were followed for five years after the first, baseline visit. They initially had a comprehensive health exam, repeated either annually or every other year between 2002 and 2009. Anyone who showed evidence of kidney disease, elevated blood sugar or triglyceride levels, or other metabolic abnormalities was excluded from the study.
There were about 900 cases of chronic kidney disease (CKD) that developed in the participants over the course of the study. And participants with higher BMIs were more likely to develop the condition than others. In particular, obese participants had 6.7 cases of CKD per 1,000 persons, while the incidence in overweight people was only 3.5 cases per 1,000. The situation was even worse for obese individuals 40 years and older 19 cases per 1,000.
"Being overweight or obese was associated with increased CKD incidence in metabolically healthy young and middle-aged participants," said the authors. "These findings indicate that metabolically healthy obese (MHO) is not a harmless condition and that the obese phenotype, regardless of metabolic abnormalities, can adversely affect renal function."
It's important to note that these data were derived from an Asian population, and the extent to which they can be generalized to other groups such as Hispanics, Caucasians or African-Americans, should be the subject of further investigations.