By Marilynn Preston

Why are Americans gaining so much weight? If we were beach balls, two-thirds of us would have exploded by now. Obesity is an epidemic, a national health problem of massive proportions and ever expanding waistlines.

But why? There have been very few (sorry, but I can’t resist) large-scale studies. Obesity experts offer up many tantalizing theories – too little exercise, too much time on our screens, useless fad diets, scam diet drugs – but very little in terms of data-based facts, a term that used to mean something.

This we know: You can’t outrun your fork. Food consumption is the primary suspect when it comes to the exploding body problem. Americans eat too much of the wrong stuff – processed foods high in sugar and naughty additives that muck up our metabolism and leave us hopelessly addicted to eating more and more.

But food is only part of the problem. There is a surprising link between the fat we are and the jobs we do. Research led by Dr. Timothy Church, an exercise researcher at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, showed that a major reason Americans are packing on the pounds is we are significantly less active in the workplace than we used to be.

In 1960, about 50 percent of workers did jobs that required moderate physical activity every day. Now, almost 60 years later, many of those lift-and-carry manufacturing and agricultural jobs have gone bye-bye, and only about 20 percent of the labor force is engaged in physically active jobs.

The rest of us – 80 percent! – are doing sedentary work that requires little more than sitting, clicking and checking messages. As a result, we’re burning, on average, 120 to 140 fewer calories every day. Day after day after day. And that, according to Church, coincides in a very significant way with the weight gain we are seeing in so many Americans.

If you suspect your job is making you fatter than you want to be, here are some strategies to help you reverse that uncomfortable slide into tighter jeans:

Reframe fitness

Stop thinking of fitness as something you do before your job or after you come home. If you want a slimmer body – and more focus – incorporate healthier choices into your workday. You know these tips by heart: Snack on fresh fruit instead of M&M’s; take the stairs instead of the elevator; do some walking as part of your lunch break. Turning a tip into an action plan is the real work ahead of you. Are you ready?

Explore what’s possible

Many enlightened companies have invested in wellness programs that include on-site gyms, healthier food choices in vending machines, meditation rooms and more. What does your company offer? Will it subsidize a health club membership? Host yoga classes at noon? If programs exist, take advantage of them. If they don’t, make polite inquiries, and join up with some health-conscious colleagues to get something started.

Reboot your commute

If you drive to work now, park in a spot that is a 10- or 15-minute walk away. Can you bike all or part of the way, perhaps using a bike carrier on your car? Many city buses carry bikes. Ditto some commuter trains. Be inventive. Be bold. Be more responsible for your own health and creative solutions will appear.

Stand up for yourself

I’m over-the-top when it comes to praising the virtues of a standing desk. Can you buy one, rig one, beg for one at work? More than 10,000 studies show all the bad stuff that happens when you sit too much. If your employer won’t pay for one, save up and get one anyway. It’s that important.

Reconsider your workspace

Abandon your office chair and sit on an inflatable ball, to build core strength and balance. Take stretching breaks every hour or so, to improve flexibility and counter fatigue. Keep light weights under your desk, and do a 10-minute routine to strengthen your arms and shoulders. When you feel stress and tension, hide somewhere to do a short calming meditation.

Keep a journal

Doing this one thing can make a remarkable difference. Write down all the food you eat while you work. Everything! Then, ask yourself why you’re gaining weight.

– Marilynn Preston is the author of “Energy Express,” America’s longest-running healthy lifestyle column. For more on personal well-being, visit www.MarilynnPreston.com.