Bariatric Surgery's Downstream Effects


Bariatric surgery is a highly effective method for weight loss compared to other interventions like exercise and dieting. While it has been shown to lead to immediate physical improvement, there is much to learn about its downstream effects.

Obesity is a growing epidemic. Since 1980, worldwide obesity has nearly doubled and now, 35% of adults are classified as overweight with a BMI over 25 while 11% are obese with a BMI over 30. These extra pounds can lead to a range of disease such as cardiovascular disease, diabetes, musculoskeletal disorders, and even cancer.


Yet, in many cases, the weight gain is preventable. Many of us around the globe live in an environment in which unhealthy foods are highly available, and technology makes exercise unnecessary. In countries like the United States, prevention techniques such as limiting caloric intake and living an active lifestyle are a large focus to face the growing size of our waistbands.

Unfortunately for those with an already expanded circumference these techniques have minimal effect. Dieting and exercise, while initially effective, usually relapse and lead to weight gain and an even a higher set weight. On the other hand, bariatric surgery, a process of removing part of the stomach to reduce nutrient absorption, has been shown to induce and maintain drastic weight loss and lead to longer survival than behavioral interventions.

While bariatric surgery leads to improvements in these parameters as well as diabetes incidence, hypertension, and lipid disturbances, there is still much to learn about the full effects of the surgery.

Early research in this topic was primarily done in male animal models showing many improvements for the animal undergoing the surgery. Yet, nearly 80% of the people getting the surgery are female. While it may be possible to extrapolate the data across genders, factors such as vast hormonal differences, which play a role in metabolism, suggest that this be done with caution. Therefore, a shift to studying the sex that is more likely to get the surgery is essential.

I recently had the fortune to meet Dr. Bernadette Grayson, a postdoctoral fellow at the University of Cincinnati, who does just that. She takes a different approach to looking at the surgery in that she looks at female animals but she also looks beyond the physical outcome of the surgery to cognitive effects and eventual effects on offspring.

In a 2013 paper, Dr. Grayson showed - in rats - that while mothers receive the health benefits of the surgery, their children tended to have set backs. These included being small-for-gestational age independently of level of dietary fat and relative glucose intolerance if their mother was maintained on a high fat diet after surgery. If these offspring were then maintained on a high fat diet, as would mimic a common modern diet, those whose mothers had undergone surgery had the greatest adiposity and poorest glucose control. This suggests that they have become more susceptible to the effects of a high fat diet.

From this, it seems that fighting obesity in one generation is inducing it in the next.

This correlation between birth weight and later problems doesn’t just exist in rats. In humans as well, it has been found that a lower birth weight can lead to a higher ratio of fat mass to lean mass as well as greater central fat and insulin resistance. It is paradoxical and yet, makes sense if you think about how the child must gain weight more rapidly to ‘catch up’ to its body’s expected weight for its age.

The cause behind the association of low birth weight and maternal bariatric surgery is still not known, but Grayson hypothesizes that maternal ghrelin may play a role. Bariatric surgeries such as vertical sleeve gastrectomy lead to a loss of most ghrelin-producing cells in the stomach and ghrelin levels have been shown to be associated with birth weight. While this needs to be further studied, perhaps some day if this is shown to have an effect, mothers who have undergone bariatric surgery can receive supplemented ghrelin to promote the long-term health of their child or perhaps bariatric surgery can be altered to promote retention of ghrelin producing cells. Until then, perhaps potential mothers should be advised against such a surgery until after childbirth.

There are a lot of strategies in place to counteract the obesity epidemic from behavioral prevention and weight loss to surgery. Yet, there is no sure way to do so. Perhaps another way we can intervene is to look to potential mothers to reduce the risk for the coming generations.


Cover Image: "A Matched Set" by Tony Alter - Flickr | Licensce: CC BY 2.0

Image: "World : Prevalence of obesity, ages 20+, age standardized: Both sexes, 2008" reproduced with the permission of the publisher, from the World Health Organization, 4 Apr 2011 (

Article last time updated on 12.12.2016.

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