How does Santa maintain his weight in the face of all those cookies?!

Dr. Jen Kerns

Dr. Jen Kerns

I am here with my tail tucked to admit that I am human: over the past 2 weeks I’ve pretty much fallen into a sugar binge. It started with Graham’s birthday cupcakes (and leftover cupcakes) with cheesecake bases and cream cheese frosting (I mean, cream cheese in a dessert is like my kryptonite!), and culminated in my cookie exchange party where I did indeed refrain from bringing any cookies home, but I probably ate 10 cookies while I was there (and drank a few glasses of my homemade egg nog before nightfall, too). I am now on day 6 of no sugar again and feeling much less mental chatter and desire, thank goodness. But man, I can do some damage when I let myself eat sugar unchecked: my weight topped out a full 4 pounds higher on a December 16, at 148.2, than it was on December 5 (144.2). That’s 4 pounds in 11 days. Granted, some of that was likely just fluid retention related to the carb loading, since I was back down 1.6 pounds within the first 48 hours of sugar avoidance, but still… I am a great example of how even “normal weight” people who are living in a weight-reduced state can continue to struggle with weight maintenance even 13 years later.


I could beat myself up about my recent Christmas cookie binge, but at least I’ve managed to eat fewer cookies than at least one other person: Santa Claus. Over the years there has been a lot of speculation about how many cookies (and glasses of milk) that Santa actually consumes each Christmas Eve as he travels around the world delivering gifts, and a very important question always results: how the heck does Santa maintain his weight?

There are a few facts that the scientific community knows to be true. 1. Santa is real. 2. Santa’s reindeer can fly. 3. Santa and his reindeer visit children’s homes century after century without apparent aging or chronic disease, despite apparently eating waaaay too much sugar.

How much sugar, you ask? A pivotal paper looking at the actual number of cookies and glasses of milk consumed by St. Nick in the United States on Christmas Eve was published in 2018 in order to calculate his total calorie intake for that evening, and found that he takes in approximately 9.9 billion kilocalories (which I call “calories” for simplicity) just during his visits to households in the U.S. alone.

PEOPLE. You don’t understand.


The authors went to calculate the calories lost to the thermic effect of food (calories burned just by digesting and metabolizing the food itself – usually around 10% depending on macronutrient breakdown), his estimated basal metabolic rate, and his total energy expenditure (which actually exceeds 54 million calories when you account for the energy it takes for him to climb up each chimney with his bag of gifts – no small feat!) , and determined that Santa’s net calorie surplus is almost 8.9 billion calories (or 2.7 million times the calories he needs to maintain his weight). The authors of this paper note that Santa returns year after year without apparent weight gain, so they throw out a few theories to explain this mismatch: that his metabolic rate is extraordinarily high, or that perhaps he underwent bariatric surgery and is experiencing a profound unexpected degree of malabsorption. However, Santa appears to be in good metabolic health with the exception of his obesity. I am here to tell you that neither of these theories hold weight (no pun intended,]: such a super high metabolic rate would require such an increase in thermogenesis (the creation of heat) that Santa would self combust and burn to a crisp, and that degree of malabsorption would undoubtedly leave signs in the form of fecal incontinence all over our fireplace hearths and gifts under the tree due to massive steatorrhea (stinky floaty diarrhea full of the malabsorbed fat). To the contrary, there are no known reports of St. Nick even using anyone’s restroom during his epic travels on Christmas Eve.

How is this possible? How can Santa remain in good health and maintain his weight year after year despite consuming billions and billions of fat and sugar calories? I suppose it’s possible that he has harnessed some elusive technology that allows him to defy our currently understood laws of physics (will you physical scientists please get on this?!), but I personally believe that the only reasonable explanation is that Santa is magical. The magic of Christmas allows Santa to remain immortal, in good health, and at a stable weight just as it enables him to visit 10,000 homes per second and travel faster than starlight (according to and NASA, respectively). Sometimes, in science, we don’t yet know the answer, try though we might. So in this case, I just choose to believe.

Merry Christmas to all!
Love, Jen




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