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Dr. Jennifer Pearlman

Health Advisor is a regular column where contributors share their knowledge in fields ranging from fitness to psychology, pediatrics to aging. Follow us @Globe_Health.

Is the progressive weight gain associated with aging inevitable? This is the question that countless patients ask of me in frustration as, despite their valiant efforts with diet and exercise, their mid-lines continue to expand.

As we age, our bodies are less responsive to the typical caloric equation of weight loss; i.e. less calories in and more calories out. Indeed, new science is revealing that age-related weight gain has very little to do with caloric balance and much more to do with the altered physiology of the aging body and adverse environmental and lifestyle factors.

By the age of 30, the body begins to undergo a dramatic change in composition, with a loss of lean body muscle, comprised of functional bone and muscle, coupled by an increase in fat mass. More and more food energy gets stored as body fat and fat stores are redistributed to the belly. Midlife weight gain continues in men until age 55, and in women until 65, when the accumulation of body fat is out-paced by an accelerating loss of lean body mass.

The health risks of adulthood weight gain have not garnered adequate public attention. More than half of middle aged Canadians now rate as either overweight or obese and as a result face increased risk of heart disease, high blood pressure, diabetes, sleep apnea, osteoarthritis, cancer and death. Obesity in women is the most important lifestyle factor that increases the risk of breast and endometrial (uterine) cancer. Women who gain more than 20 pounds from the age of 18 years to midlife double their risk of developing breast cancer compared to those who maintain stable weight.

The growing problem of midlife weight gain is in part the result of our failure to recognize and address qualitatively, instead of quantitatively, the root causes. We think in terms of calories in our diet and pounds on our scale instead of the quality of our food and the composition of our bodies. But new research is unravelling the complex causes of midlife weight in terms of genetic predispositions and metabolic derangements, coupled with lifestyle and environmental factors. Instead of the caloric equation, age-related weight gain may be better explained by the loss of vital factors such as hormones, nutrients, sleep, insulin sensitivity and metabolic efficiency coupled with a gain in stress, unfavourable gut bugs, and environmental toxins. Let's take a closer look at some of these more unknown factors.

Our DNA is not our destiny, but it is a road map The risk of obesity and diabetes is partially encoded in our DNA. While several gene suspects have been previously identified, scientists have recently uncovered perhaps the king of obesity genes – one that directly links weight and metabolic dysfunction to environmental factors. Early this year, scientists confirmed a novel fat gene, IRX3, which increases the risk of diet induced obesity and diabetes. The research shows that mice with two copies of the IRX3 gene, when fed a high-fat diet, faced a 50 per cent increased risk of obesity and a 70 per cent increased risk of diabetes.

Our bugs matter While gene-environment interactions confer increased risk of age-related weight gain, so too do our body's bugs, collectively referred to as the microbiome. Yes – our bugs matter! Indeed, only 10 per cent of the genetic material inside our bodies belongs to us and the balance belongs to the bugs in our guts. The microbiome is comprised of bacteria that co-habitate our bodies, many of which are critical to our survival. Dysbiosis is the overgrowth of pathogenic or unfavourable bacteria and has been implicated in auto-immune disease, asthma, diabetes, cancer and obesity. Recent research has shown that gut bugs play a vital role in energy extraction, storage and expenditure and contribute to diet-related obesity. The high fat, high sugar Western diet triggers an overgrowth of a group of bugs known as the Firmicutes which are better equipped at harvesting the refined sugars that make up the Western diet, importing glucose into the body and converting it to fat. Studies have shown that compared to an ideal low fat, high fibre diet, the Western diet yields loss of healthy gut bugs (such as bacteroidetes) and overgrowth of Firmicutes. So not only do our genes matter, but our bugs too can affect weight gain.

Obesogens: the solution to pollution is dilution Environmental factors have the potential to influence both the expression of our genes and the type and diversity of our bugs. Since the end of the Second World War, over 80,000 industrial chemicals have been pumped into our environment. The increase in synthetic chemical production has coincided with a dramatic rise in the prevalence of obesity. Mounting scientific evidence suggests many industrial chemicals are obesogens, having the potential to alter metabolic function and lead to weight gain. And as the solution to pollution is dilution; more obesogenic toxins yields more body fat. Persistent organic pollutants such as organo-chlorine pesticides and polychlorinated biphenyls (PCBs) have been strongly linked with metabolic derangements in humans including diabetes and obesity. These types of environmental hazards are found pervasively as pesticides on our produce and chemical agents in our plastics but also will bioaccumulate into the fat depots of large animals.

Stress alters dietary decisions The environment is not just chemically toxic, but also socially and physically. In our 24-7 connected world of incessant multitasking, we end up over-stressed and under-slept. Too much cortisol and insomnia contribute to weight gain and altered signalling making us more vulnerable to the relentless marketing of shelf-stable, readily accessible processed foods high in refined grains, trans-fats, and prone to consuming more liquid calories than ever before.

Qualitative solutions for frustrated dieters The qualitative new paradigm requires careful attention to novel risks for weight gain. And so to the frustrated midlife dieter, I will encourage a rethinking of calories, a qualitative dietary shift to up the essential building blocks for lean body mass (i.e. healthy fats and lean protein), and a redesign of lifestyle to stress less, sleep better and minimize environmental toxic exposures. While we can't fix our genes, we can shape our environment to help us achieve and maintain our optimal health and shape.

Dr. Jennifer Pearlman is a physician focused on women's health and wellness and a staff physician at the Menopause Clinic at Mount Sinai Hospital in Toronto and Medical Director of PearlMDRejuvenation, a women's health and wellness facility. You can follow her on Twitter @drjpearlman.