03/25/2014 01:38 pm ET | Updated May 25, 2014

Weight-Loss Resistance and Choices

Weight is not a behavior, and weight is not a choice. Nobody wakes up and decides what to weigh today. In an age when healthy and unhealthy behaviors are increasingly subject to incentives and disincentives, respectively, this is all too easily forgotten.

Of course, weight is largely the byproduct of behaviors and choices, namely what and how much we eat, and what and how much we do: calories in and calories out. But the simple math of energy balance and the simple premise that our choices are in charge of it are complicated by two considerations.

First is that the choices we make are in turn dependent on the choices we have, and in the case of energy balance, all of modern culture conspires against good choices. In particular, foods designed to be all but addictive and maximize the calories it takes to feel full -- designed with the aid of such powerful technologies as functional MRI scanning no less -- are a potent sabotage of personal responsibility and good choices.

Second, two people may make the very same choices and wind up at very different weights. As a clinician with some 25 years of direct patient care experience, I can say categorically that two people can eat the same amount and exercise the same amount, yet one gets fat and one stays thin. This, of course, is not at all fair. But we have all, I trust, been around that block a time or two. We know life isn't necessarily fair. Or at best, it's fairly unfair over time, as bad things happen all too often to thin people, too.

Let's quickly acknowledge that differential weight outcomes despite comparable diet and activity levels do nothing to repudiate the laws of thermodynamics. The relationship between matter and energy characterized initially by Newton is a basic tenet of physics, and all but unassailable. Certainly, it is stationed well above the pay grade of New-Age iconoclasts who debate the relevance of calories to no valuable end. Yes, calories do count. They are a measure of energy, and anyone wanting to contest the relationship between energy and matter has to go toe to toe with Sir Isaac. He's never lost yet.

There is no need to revisit laws of physics to explain the paradox of differential weight outcomes. We need only visit the local car dealership. We are well accustomed to the list of attributes highlighted when cars are on sale, and among these is fuel efficiency. Obviously, it varies. That does not alter the properties of the fuel. It does not challenge the reliable meaning of a gallon or liter. It merely indicates that not all engines are created equal.

That is exactly true of the human engine, our metabolism, as well. We vary markedly in fuel efficiency due to various factors. Some are as obvious as our heritage. There are whole populations, such as the Pima Indians of the American Southwest (and originally, Mexico) whose ancestors adapted to survive in a very frugal desert environment, who are remarkably fuel efficient. Such groups, notably including many Native Americans and Pacific Islanders such as the Samoans, gain weight with stunning ease when exposed to modern living, and shed pounds very laboriously.

Underlying such ethnic variation is, of course, genetic variation -- so variable response to particular doses of calories in and calories out is partly explained by genes. It is partly explained by body composition as well, which is in turn partly explained by still other genes, as well as experiential factors. A higher mass of muscle increases the calories needed to maintain weight. A lower mass of muscle and higher fat content has the opposite effect.

And then still other factors, some known and some doubtless yet unknown, influence weight outcomes in ways we are just beginning to appreciate. One that is well established is hormonal responses, in particular that of insulin. People who need higher levels of insulin to maintain normal blood sugar are preferentially disposed to deposit calories into body fat and gain weight. Weight gain then tends to worsen insulin resistance, and this very readily becomes a degenerating and very frustrating, spiral.

A more recent and increasingly salient consideration is the status of our microbiome, the bacteria that colonize our bodies, and especially our gastrointestinal tract. We have long known that bacteria outnumber our cells roughly 10 to one, and figure importantly in digestion. We are learning all the time how important they are to other body functions as well, from immune responses to hormonal balance.

One of the new frontiers in medicine is the recognition that significant alterations of the gastrointestinal flora can produce significant alterations in weight. In some cases, it can apparently result in extreme weight-loss resistance.

I have had patients in this category, people who eat very frugally, exercise strenuously and just can't seem to take off weight. Of course, sometimes people seemingly in this category are telling themselves and their doctor, perhaps inadvertently, little white lies -- exaggerating how few calories they consume, or how much they exercise. But among my weight-loss resistant patients are some who have undergone full metabolic testing, verifying the truth of their claims. Some people are almost shockingly fuel efficient, vulnerable to weight gain and resistant to weight loss.

This frustrating problem prompted me to create an online exchange for those affected, so a community could come together and benefit from the 'hive mind.' I invite any in this camp to visit the site, and I invite experts in this area to contact me via email to explore the possibility of sharing that expertise. My thanks in advance to those who do so.

There are cases, few and far between thus far, where extreme weight-loss resistance has been linked to disruption of gastrointestinal flora, due to antibiotics or some other trauma. And, in some cases, the still extreme option of fecal transplant -- introducing a full suite of normal intestinal bacteria -- has proven therapeutic. Lesser instances of the same basic problem may respond well to probiotics, prebiotics or a combination.

In some cases drugs, such as the diabetes drug metformin, may prove useful: metformin enhances insulin sensitivity, and has a potential role in treating insulin resistance in addition to diabetes. In some cases, nutrient supplements may be appropriate. Cinnamon can help stabilize blood sugar and insulin levels. Green coffee bean extract appears thus far to be a safe and effective means to boost metabolism slightly. Garcinia cambogia may help attenuate appetite, among other effects. A product called PGX made from dietary fiber can blunt the glycemic effect of food.

The right response to weight-loss resistance will vary. In some cases, it will be learning to love the skin you're in -- not everyone who wants to lose weight really needs to do so. If you carry extra pounds but are fit and vital and healthy, perhaps you can and should learn to accept rather than fight your "natural" weight, shape and size. Your life may be better if you do.

For those who can't or won't accept their weight, or whose health is compromised by it, the options for addressing weight-loss resistance should be explored with a health care professional who knows what they are doing. The approach should be individualized, and given the limits to our current knowledge, will likely involve some trial and error. But it can result in success, so keep the faith.

Weight-loss resistance is real. I've seen it, up close and intimately.

Weight, per se, is not a choice. Addressing the variable challenge of weight management with insight, understanding and compassion certainly is. It's a choice we should all be making.



Dr. David L. Katz is President of the American College of Lifestyle Medicine.

Author, Disease Proof