Arya M. Sharma, MD

I am currently attending the 8th Academic Board Members Meeting of the International Chair on Cardiovascular Risk here in Boston. As always, Jean-Pierre Després (Université Laval), the Scientific Director of this chair, together with the local host, Peter Libby (Brigham and Womens, Harvard), have put together a remarkable program on the role of abdominal obesity in cardiometabolic disease - this time the focus is on inflammation.

Readers of these pages, will be familiar with previous posts on the possible role of inflammation in the development of obesity related complications. This state of low-grade chronic inflammation is particularly found in people with visceral or ectopic fat.

In his presentation, Gokan Hotamisligil (Harvard School of Public Health) used the term “metainflammation” to describe this state of low-grad inflammation that leads to inflammatory response in many tissues and has been postulated to play an important role in the many metabolic alterations like insulin resistance, type 2 diabetes, but also atherogenesis in blood vessels that can ultimately precipitate a stroke or heart attack.

I was particularly enamored by the Jean Vague/Per Bjorntorp Award Lecture presented by Wilfred Y. Fujimoto, Professor Emeritus of Medicine, University of Washington, who talked about his remarkable long-term studies on Japanese Americans in which, using sequential computer tomography, his group was able to demonstrate the important role of visceral fat for the striking propensity to develop type 2 diabetes in this ethnic group.

Clearly, this is an area of research, where much remains to be done before we fully understand why some people are more prone to the cardiometabolic complications of obesity than others.

Click here for more on the various activities of the International Chair on Cardiometabolic Risk.

AMS
Boston, MA

Regular readers of these pages are well aware that when it comes to health risks, not all fat is bad.

We now know that for many conditions like diabetes and heart disease, increased fat deposits inside your abdomen and in organs like the liver, heart or skeletal muscle are the real problem.

In contrast, there is increasing evidence that fat deposits under the skin (particularly on hips and thighs) may actually reduce the risk of these conditions.

Simply put, it appears that there is good and bad fat - which is why obesity is not all the same and BMI alone is not a good measure of health.

It now seems that the same ying-yang of visceral and subcutaneous (sc) fat may also apply to the relationship between obesity and bone health.

This notion is supported by data just published in the Journal of Clinical Endocrinology and Metabolism by Vicente Gilsanz and colleagues from the University of Southern California, Los Angeles, USA.

Gilsanz and colleagues studied the relationship between sc and visceral adiposity and the cross-sectional dimensions and other characteristics of the femur (thigh bone) in 100 healthy women between 15 to 25 years.

After multiple adjustments for leg length and thigh musculature, both sc and visceral fat had strong and independent associations with femoral cross-sectional area, cortical bone area, and various other measures - but in opposite directions!

Whereas sc fat had a strong positive relationship to all femoral bone characteristics, visceral fat had a strong negative effects on these parameters - or in other words - sc fat good, visceral fat bad.

Although the authors can only speculate on the reasons for this paradoxical relationship between fat depots and bone health, the data clearly suggests that as for diabetes and heart disease, when it comes to the relationship between fat and bone health, the old real estate mantra applies: location, location, location.

AMS
Edmonton, Alberta

Body weight is one of the most highly regulated genetic traits.

This is perhaps best demonstrated by the fact that it is almost impossible to find genetically identical individuals (or monozygotic twins) with marked differences in body weight.

In contrast, it is much easier to find non-identical twins (who only share some of their genes but the same environment) with great differences in body weight.

Despite this strong influence of genes on body weight, lifestyle can very much make a difference.

This was now demonstrated by Tuija Leskinen and colleagues from the University of Jyväskylä, Finland, who after combing through thousands of twin pairs from the Finnish Twin Cohort, identified seven genetically identical (monozygotic) and nine non-identical (dizygotic) middle-aged (50-74 years) same-sex twin pairs who reported a long-term discordance for physical activity (International Journal of Obesity).

Irrespective of the genetic make up, the physically inactive co-twins had a 50% greater visceral fat area, a 170% higher liver fat score, and 54% more intramuscular fat.

This study clearly demonstrates that even in individuals who share the same genes and/or similar childhood environments, regular physical exercise can prevent the accumulation of high-risk fat over time.

Thus, whatever your genetic background or early childhood environment, it is better to be regularly physically active than sedentary (who would have guessed?).

AMS
Edmonton, Alberta

Last week I blogged about an article by Jennifer Kuk, (York University, Toronto) on the effect of weight satisfaction on healthy behaviours.

Now Jennifer is back, with her Mentor Bob Ross (Queen’s University, Kingston, Ontario) with an article on sex differences in regional weight loss between obese men and women, published in the International Journal of Obesity.

In this study, Kuk and Ross examined changes in total, subcutaneous, and visceral (intra-abdominal) fat using sophisticated magnetic resonance imaging (MRI) in 81 men and 72 women who had participated in various diet and/or exercise interventions at Queen’s University, Ontario, Canada.

Although, there was a significant correlation between weight loss and reductions in waist circumference with changes in total, subcutaneous, and visceral fat, for a given weight loss, men had a significantly greater decrease in waist circumference and visceral fat than women - the greater the weight loss, the greater the sex difference in loss of visceral fat.

These finding may have important clinical implications: as most of the metabolic complications of obesity are associated with excess visceral rather than subcutaneous fat, it appears that for the same amount of weight loss, the health benefits may be greater for men than for women.

Given my previous posting on why women are more likely to gain weight and may have a harder time losing it, guys seem to come out of this with a clear advantage.

This said, it continues to be disconcerting that most obesity programs consistently report an overbearing majority of female patients (generally over 80%) - the guys appear far less concerned about or interested in losing weight.

Perhaps the news that men who lose weight, are more likely to lose the “unhealthy” visceral fat, may drive more men to seek obesity treatment - if so, I’d be very surprised!

AMS
Edmonton, Alberta

Most people by now realize that visceral (intra-abdominal) fat accumulation is an important determinant of the cardiovascular and metabolic risk associated with excess weight (Visceral Fat Fattens Carotid Arteries, Jan 16, 2009)

The omentum is a large apron of fat inside the abdomen, which accounts for a large proportion of visceral fat. It is therefore only natural to ask the question whether surgical removal of this fat depot would be beneficial in patient with visceral obesity.

This question was now addressed in a randomized controlled trial in patients undergoing gastric bypass surgery for severe obesity (Obesity Surgery, April 2009).

In this study, Attila Csendes and colleagues from the University of Chile, Santiago, Chile, randomized 70 patients to laparotomic (open) resectional gastric bypass and an omentectomy.

Two years after surgery, no differences were seen in BMI levels in either group. Blood sugar levels, serum insulin, total cholesterol levels, serum triglycerides and blood pressure were similar in both groups.

Based on these results, omentectomy is not justified as part of bariatric surgery.

Given that previous small case series suggested that there may be some advantage to omentectomies, the “negative” results of this study documents the importance of conducting prospective randomized controlled studies.

AMS
Edmonton, Alberta