It seems these days that everyone is on a special diet of some sort. Roz Chast has a wonderful cartoon titled “The Last Thanksgiving,” which depicts a dozen or so people around a dinner table, each with a special dietary need. The implication is that this holiday has become so complicated that we may soon end it. Diets used to be pretty much restricted into a few broad categories: weight loss, vegetarian, and religious. Even weight loss diets were not nearly as popular as they are now. The first sugar-free soft drinks were not introduced until the 1960s. Back then, weight loss was considered a matter of calories in/calories out. All one needed to do was to balance that equation and slimness could be yours: potatoes=bad, grapefruit=good, etc.

We now understand that equation to be faulty. The vast majority of people who lose weight will gain it back, regardless of what kind of program they adopt. It seems that this issue is quite a bit more complicated: individual physiology, including genes, hormones, and even bacterial content of our guts may play a role in determining weight. A new study that may shed light on this complexity was just reported last week. Doctors are studying a young woman in Texas who suffers from “neonatal progeroid syndrome.”  This is a condition resulting from damage to just one gene, causing facial deformities and destroying the layer of fat under the skin. Crucially, it has been discovered that this gene interferes with the body’s ability to make a hormone called asprosin, which regulates blood sugar. What this means practically speaking is that though she is always hungry, she can’t eat more than a few bites without feeling full and so she is unable to maintain a healthy weight. Studying this newly identified hormone, asprosin, in mice, scientists have already gained some insights into how weight regulation may be improved for humans.

Meanwhile, we are left trying to find an individual path to dietary balance, and those paths are proliferating. About a decade ago, encountering food expert Michael Pollan at a party, I besieged him with questions having just read his latest book, “The Omnivore’s Dilemma” (2006). He graciously spoke with me about the various issues he had raised: grass-fed beef, organic vegetables and fruits, etc. Before reading his work, I had not completely understood all of the issues involved in some of these choices. For example, I had always thought that organic foods were better for you because they were pesticide-free, and thus less harmful.  Pollan’s book explained why non-organic foods are also less nutritious because of various changes that occur when additives, etc., are involved.

Pollan raised another issue that he said he was seeing more and more: orthorexia, a preoccupation or obsession with eating “the right foods.” Though he has tried to simplify our approach to healthy eating (having famously advised us to “Eat food. Mostly plants. Not too much.”), he saw his work unintentionally sparking fads or even obsessive diets. Pollan worried that things were going a bit too far, and that an interest in good diet was fueling neuroses. Since that time, his fears have been more than realized as new regimes are touted weekly and others, like gluten-free diets, are becoming commonplace. The evidence for the need for some of these restrictions is sometimes contradictory, as in the vegan diet (which restricts all animal foods, including dairy) vs. paleo diet (which advocates eating like a cave man, emphasizing meat).

Everyone seems to agree on the health benefits of nuts, it seems, except that nut-allergies have proliferated in recent decades and can be deadly. One of the problems with so many people jumping on the “sensitivity” bandwagon is that it may desensitize us to those who have life-threatening allergies. Some of these, like nut allergies, are lethal and require the intense scrutiny and cooperation of everyone in the community to manage. But others’ food “issues” are more a matter of preference, or even experimentation.

Reporting on the difficulties of catering to special diets in families, The New York Times warned last week that holidays are even more stressful when special diets become an issue. The Times writes: “One in six parents has a teenager who has tried either a vegetarian, gluten-free, vegan or paleo diet within the last two years, according to a new survey of 910 parents of teenagers from the University of Michigan C.S. Mott Children’s Hospital. The parents were a nationally representative sample, and all had at least one child between 13 and 18.”