With never-before-seen weight loss efficacy of new and emerging weight management medications, I’ve seen this question recently come up in both social media and mainstream media:


Can a person become malnourished due to weight loss medication?


The World Health Organization actually defines malnutrition as encompassing both undernutrition as well as overweight and obesity.  For purposes of today’s discussion, we are talking about undernutrition.


Most approved weight loss medications work by reducing appetite, and some also work by decreasing cravings.  Food preferences can change, typically in a good way (with less desire for high fat/high sugar foods).  These effects can be highly variable from one person to the next, and cannot be predicted.  If appetite is suppressed dramatically, intake of nutrients could plausibly fall below nutritional needs.


As blogged previously, with weight loss by any treatment modality, about two thirds of weight is lost as fat, and about one third as lean mass (muscle).  Ensuring adequate protein intake is important to give the body the building blocks it needs to avoid excessive muscle loss.


While deficiency of specific micronutrients (vitamins or minerals) is not known to occur with weight loss medications (with the exception of orlistat – see below), it makes sense to have a dietitian or nutritionist on board with you to periodically evaluate your diet and ensure you are getting the nutrients you need.  (Note: as orlistat works by reducing fat absorption in the gut, people taking orlistat are at risk of deficiency in the fat soluble vitamins (A, D, E, and K).   A multivitamin is recommended for most people taking orlistat.)


If weight loss medications are prescribed inappropriately to people without obesity, perhaps those people are at higher risk of undernutrition.  We don’t have clinical trial data on this and we never will, as it is not appropriate to prescribe obesity medication to people who don’t have obesity to begin with.

A person can lose excessive weight with weight loss medication, and if this is happening, the dose of medication should be decreased until the person comes back up to a healthier weight.  In fact, we need to think of obesity medication as titratable to effect from the outset.  One dose does not fit all.  Until the recent advent of more effective medications, weight loss medications were generally prescribed with the goal of getting to the highest dose, which typically achieved around 5-10% weight loss.  With new and emerging medications that can achieve an average of 15-20+% weight loss, we need to shift our thinking to helping people find the right dose to meet their weight management goals (defined as improvement in health, not solely/necessarily the numbers on the scale).


BOTTOM LINE:  For anyone on a weight management journey, it’s important to ensure you are getting adequate nutrition.  Working with a dietitian or nutritionist to periodically evaluate your nutritional intake is always a good idea.


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