In 1960, the average American man was 5'8" and weighed 166.3 pounds. The average woman was 5'3" and 140.2 pounds.

Today we’re about an inch taller (5'9.3" for men and 5'4.8" for women) and a lot heavier (195.5 and 166.2 pounds, respectively – an increase of 26-30 pounds). A lot of that extra weight is unhealthy belly fat: Waist circumferences for men/women now average 39.7/37.5 inches.

Nearly 70 percent of adults are overweight, and a record 38 percent are obese. The basic equation in weight gain is taking in more calories than are burned off. But there is increasing awareness that it’s not that simple, that overeating and inactivity are not the only factors in our epidemic of obesity. Let’s look beyond the obvious.

More than calories in/calories out

There is no doubt that we are more sedentary than we used to be. In 1960, one in two jobs required at least moderate physical activity, compared to just one in five today. We walk less and drive more, even to nearby destinations. Back then, half of all kids walked or rode their bikes to school as opposed to just 13 percent nowadays.

We are also eating up to 400 more calories per day than we did 50 years ago. We dine out more often, portion sizes are larger, especially in restaurants but also at home, and inexpensive, calorie-laden foods and drinks are everywhere.

But it’s not just a question of calories. We’re also eating fewer whole, nutritious, naturally satiating foods and more high-calorie, nutrient-depleted processed items loaded with ingredients that pack on the pounds. For example, 13 percent of our calories come from added sugars such as high-fructose corn syrup, which is particularly adept at promoting fat storage.

Gut microbes and weight

Another casualty of an unhealthy diet is our gut microbiota, the trillions of microorganisms that reside in our intestinal tracts. Fiber-rich plants and fermented foods nourish gut bacteria, but these foods have taken a backseat in the average American diet, and it’s impacting our weight. Gut bacteria not only aid digestion but also influence appetite, fat absorption, metabolism – and whether we’re heavy or thin.

Everyone has a unique microbiota, but there are marked differences in the microbial makeup of lean versus obese people. Normal weight individuals have considerably more bacterial diversity and higher concentrations of types like Bacteroidetes, which break down fiber and starches.

Diet isn’t the only culprit. Antibiotics, which are overprescribed by doctors and inappropriately used to fatten up livestock, also alter the gut microbiota and likely contribute to our growing girth.

Are your drugs making you fat?

Antibiotics aren’t the only problematic drugs. Many medications increase appetite, promote fat storage, or slow metabolism and list weight gain as a side effect. Three out of five Americans take at least one prescription drug, and use of multiple medications has nearly doubled in the past decade.

Antidepressants, which are taken by one in 10 people and one in four middle-aged women, increase weight in most of those who use them, and about 25 percent put on 10 pounds or more. Antipsychotics are even worse; a gain of 10 pounds during the first couple of months and 25–35 pounds over a year is not unusual. These potent meds used to be prescribed only for people with serious mental illnesses like schizophrenia, but today they are bestselling drugs for depression.

Insulin, used by nearly 30 percent of people with type 2 diabetes, is notorious for weight gain. I’ve had patients who put on as much as 100 pounds while taking insulin! With the exception of metformin, oral diabetes drugs are associated with weight gain as well.

Other classes of drugs that increase the odds of gaining weight include steroids, statins, beta-blockers, birth control pills, antihistamines, and anticonvulsants.

Why sleep matters

Inadequate sleep is also linked with weight gain, and we’re definitely sleeping less than we did in the past. Average sleep duration in the 1960s was more than eight hours; today it’s six and a half, and 30 percent of us get fewer than six hours.

Sleep deprivation or disruption causes changes in hormones that affect appetite and fat storage. It reduces leptin, which signals when you’re full, and increases ghrelin, the “hunger hormone” that stimulates appetite. Cortisol, a hormone released in response to stress, also rises, contributing further to increases in appetite and storage of visceral (abdominal) fat.

The most serious sleep disorder, sleep apnea, is closely tied to obesity, but is it the chicken or the egg? Obesity is clearly a risk factor for sleep apnea, which causes periods of breathing cessation and precipitous drops in oxygen. However, it goes both ways. Sleep apnea disrupts the deep, restorative stages of sleep and worsens these metabolic and hormonal changes, making weight control all the more challenging.

Toxins may play a role

More than 85,000 industrial chemicals are in use in the US, but only a few hundred have been tested for safety. The health effects of even low-level exposure are unknown, but mounting research suggests that some of these chemicals are implicated in obesity

Of greatest concern are endocrine disruptors, which interfere with the signaling of hormones and adversely affect growth, development, and metabolism. These chemicals are everywhere – in plastics, food containers, flame-retardants, heavy metals, pesticides, and more.

Levels in animals and humans have been steadily increasing for decades, and studies show that concentrations are higher in obese individuals. Scientists are particularly worried about fetal and early childhood exposure and increased risk of obesity later in life.

Other weighty contributors

There are a number of other factors that may also contribute to obesity. Some researchers suspect certain viral infections. Others point to prenatal influences, such as maternal obesity or malnutrition. Increased use of central heating and air-conditioning has been proposed, because it reduces the need to burn energy maintaining normal body temperature. Genetics and epigenetics, the switching off or on of genes that can be passed down from one generation to the next, also play a role.

The take-home message is not that any one of these is the answer. Diet and exercise are still the most powerful tools for achieving and maintaining optimal weight. But even if the impact is small, the cumulative impact may be significant. It’s time we get a handle on this health crisis, and tackling all potential risk factors is as good a place as any to start.

Recommendations

• Exercise and diet are essential for weight loss and maintenance. Although most any program will work as long as you stick with it, I recommend the mini-fast with exercise because it doesn’t require dramatic calorie cutting, targets fat burning, and improves multiple aspects of health. Visit drwhitaker.com or read The Mini-Fast Diet to learn more.
• Support optimal gut bacteria by eating lots of fiber-rich vegetables, fruits, beans, etc., yogurt and other fermented foods, and taking probiotic supplements.
• Talk to your doctor about reducing your medication load. Natural alternatives are available for virtually all health challenges.
• Do whatever it takes to improve your sleep, including getting tested for sleep apnea.
• Avoid obvious exposures to environmental toxins, and consider chelation for serious detoxification.