How the workplace contributes to America's expanding waistlines

An annual survey by Careerbuilder.com finds that the stresses associated with full-time employment may contribute to obesity.

The survey sampled more than 3,000 full-time workers across a variety of industries in the U.S. Seventy percent of people with extremely stressful jobs were overweight, compared to 47 percent of people who reported extremely low stress levels at work. Nearly half of all workers surveyed said that they've gained weight in their present job, with 20 percent reporting weight gain in excess of 10 pounds.

"When we're stressed we want to eat for comfort," registered dietician Tanya Zuckerbrot told CBS News. "We want to feel soothed and calmed and relaxed, so we turn to sugary, caloric foods such as a muffin or some chips."

Although about a quarter of U.S. workers have access to employer-sponsored gyms including onsite workout facilities, 63 percent say they do not take advantage of them, claiming to be "too tired from work to exercise."

Mid-career workers were the most prone to weight gain, possibly a result of increased stress as they move up the career ladder as well as the typical age-related slowdown in metabolism.

"It's your habits within the workplace that really contribute to how much weight you're gaining," Zuckerbrot said. She offered tips to avoid workplace weight gain, which include packing lunch and snacks instead of going out or hitting the vending machines; passing on co-workers' birthday cakes; and ditching coffee and sugary sodas.