Nephrol Dial Transplant (2004) 19: 1934
Nephrol Dial Transplant Vol. 19 No. 7 © ERA-EDTA 2004; all rights reserved
Letter
After all those fat years: renal consequences of obesity
Sir,With interest we read the editorial by Wolf on obesity as a renal risk factor [1]. We fully support the author's view that overweight and insulin resistance, as mediators of renal risk, deserve attention not only in morbidly obese patients with overt insulin resistance, but also in renal patients with less severe obesity.
Recent data from our group suggest that the impact of overweight and insulin resistence may be even larger, and relevant to subjects without overt obesity. First, we found that the relationship between body mass index (BMI) and renal haemodynamics is already apparent in subjects without overt obesity. In 102 healthy subjects with a mean BMI of 24.8 (range 16.1–29.7) kg/m2, a higher BMI was significantly associated with a higher filtration fraction, without a threshold value. Thus, the balance between afferent and efferent glomerular arteriolar tone is unfavourably altered at values of BMI below the overtly obese range [2].
Moreover, epidemiological data from the general population suggest that the effect of insulin resistance may also extend beyond overt obesity. In the PREVEND cohort (7676 subjects), a higher waist–hip ratio, as an indicator of insulin resistance, was associated with impaired renal function—not only in obese but also in lean subjects—defined as a BMI <25 kg/m2 [3], suggesting that insulin resistance can affect renal function in the absence of obesity. This association was independent from other risk factors, such as hypertension and micro-albuminuria.
The data suggest that the mechanisms present in obese, insulin-resistant renal patients can also be encountered in subjects without overt obesity according to current definitions, and may adversely modify the course of renal function loss. As noted by Wolf, it would be premature to make general recommendations. In particular, the relationship between BMI, nutritional status and overall risk profile in renal patients may not be similar to that in non-renal populations. Nevertheless, the data so far indicate that mechanisms present in overtly obese and/or insulin-resistant subjects may be relevant in much larger populations than assumed so far—and definitely deserve further exploration as to their relevance in renal patients.
University Medical Centre Groningen Department of Internal Medicine Groningen The Netherlands Email: r.j.bosma{at}int.azg.nl
References
- Wolf G. After all those fat years: renal consequences of obesity. Nephrol Dial Transplant 2003; 18: 2471–2474
[Free Full Text] - Bosma RJ, Homan van der Heide JJ, Oosterop EJ, De Jong PE, Navis GJ. Body mass index is associated with altered renal hemodynamics in non-obese healthy subjects. Kidney Int 2004; 65: 259–265[CrossRef][Medline]
- Pinto-Sietsma SJ, Navis GJ, Janssen WM, De Zeeuw D, Gans ROB, De Jong PE. A central body fat distribution is related to renal function impairment, even in lean subjects. Am J Kidney Dis 2003; 41: 733–741[Web of Science][Medline]
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