Obesity's Damaging Effects On The Kidneys

Being fat greatly increases risk of developing kidney disease

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Quinn Dombrowski; Flickr.com; Creative Commons 2.0 License

I probably don't need to start off with the usual platitudes about obesity's damaging effects on your health. A grand simplification would be a two word long statement: "obesity kills". But most people know that already. Obesity's role as a major risk factor for heart and cardiovascular disease, diabetes, bone and joint disease are almost universally known. 

WE ARE GROWING FATTER

In 1997, the World Health Organization called obesity "one of the greatest neglected public health problems of our time with an impact on health which may well prove to be as great as that of smoking".

If you are in to statistics, here are some sobering numbers: close to 3 million people die each year because of being obese. To give you a perspective, that is about a fifth of the number of people who died in World War II (15 million). In other words, we are losing the same number of people to obesity every five years, as died during the war! We, the Land of Plenty are the fattest nation in the world by sheer numbers (although American Samoa takes the cake if you go by the percentage of obese population).

Why we have this dubious distinction is beyond the scope of this article, but it includes social, cultural, and economic factors. We live in an era of cheap food and large portion sizes. What is a small in the US is a large in Europe. What is a medium in the US does not exist in most other places on Earth. This epidemic of gluttony is bound to have public health effects. 

DOES OBESITY HURT YOUR KIDNEYS

Absolutely.

Over the last decade, several studies have established higher body weight for height (your Body Mass Index) as a risk factor for kidney disease development and progression. This stands true even after adjusting for blood pressure and diabetes. In other words, people who are obese are at risk of developing kidney failure because of their obesity alone, and not just because they are also more likely to have high blood pressure and diabetes (otherwise the two biggest risk factors for kidney disease).

 

Another over- simplification would be to state that: the heavier you are, the harder your kidneys work. From a more scientific standpoint though, obesity induces a range of dysfunctional changes in the kidney that eventually lead to chronic kidney disease (CKD). In the worst case scenario, the affected person could see their kidney function decline to the point where they need dialysis.  

So what are these changes. At the risk of getting too technical, let me give you a quick overview:

  1. Obesity already has a known association with other diseases that hurt your kidneys. I am talking about the usual suspects- high blood pressure, diabetes, high uric acid levels, high cholesterol levels, etc. This constellation which often comes as a "package deal" with obesity is called the metabolic syndrome. These conditions lead to kidney disease, albeit by indirect mechanisms.  
  2. Obesity directly causes damaging changes in the kidneys' blood perfusion and pressure. These changes begin long before any clinical effects of obesity on the kidneys are obvious. This was shown in a major study from Spain that did kidney biopsies on obese patients presenting for weight loss/bariatric surgery.
  1. If you thought that your body fat which you happen to hate so much is merely a passive depot of tissue that prevents you from showing your six-pack, think again. The new paradigm in our understanding of body fat is to view it as an endocrine gland; one that produces hormones called "adipokines". It is these adipokines that cause systemic inflammation and alteration in the kidneys' blood flow/pressure. Inflammation hurts the blood vessels and kidneys, among other organs. When cells in the kidney die from the effects of this inflammation, it could lead to permanent scarring in the kidneys which eventually leads to kidney disease. Hence, body fat is a thriving nidus of hormonal activity that is harmful for the kidney function. 

​IS OBESITY RELATED KIDNEY DAMAGE TREATABLE 

The no brainer answer would be that losing weight might help. Weight loss is known to reduce blood pressure, drop your insulin resistance, and reduce the systemic inflammation mentioned above. Beyond losing weight though, a few medications might have a role in certain situations:

  • For instance, a specific kind of kidney disease caused by obesity is something called Focal Segmental Glomerulosclerosis (FSGS), and it might be possible to control that in the early stages by medications called ACE inhibitors (an example would be lisinopril).
  • Cholesterol medications like statins might be helpful (eg. atorvastatin or Lipitor).
  • Metformin, a common medication used for diabetes has a role in preventing obesity related kidney damage
  • Treatment of associated risk factors like hypertension, diabetes or insulin resistance, sleep apnea, dyslipidemia is also necessary. 

​Long story short, being fat is bad news for your kidney function. Tighten your belt if the thought of being on dialysis scares you. 

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