Choosing the right foods for snacks can determine whether older Americans have a healthy diet and maintain or lose weight. Lifestyle changes give retirees more free time and, naturally, more time at home. Some seniors find themselves opening the fridge door as often as a teenager. For better health, it’s important to take charge of snacking.

“Seniors have a couple of issues that make them different from the standpoint of putting on weight,” says Dr. Rick Gallop, former president of the Heart and Stroke Foundation of Ontario and author of “The G.I. Diet” (Workman Publishing).

“They have a reduced activity level — women are no longer running around multitasking at home. They face a loss of muscle mass, beginning at age 40 for women and 60 for men. Women have menopause and these hormonal changes slow down the metabolism, so they’re not burning as many calories.”

Snacks play a significant role in keeping the digestive system busy, Gallop says. He recommends three snacks a day — at midmorning, afternoon and before dinner.

“My grandmother was always saying, ‘The devil finds work for idle hands,'” Gallop says. “Well, if the tummy is not doing something, it’s looking for its next meal.”

To avoid letting an idle stomach wreak havoc on an otherwise healthy diet, snack time must not become treat time. Gallop struggled to lose weight as an older man. At 60, he lost 20 pounds and has kept it off. His experience led him to write a simple-to-follow diet book based on the Glycemic Index, or G.I.

“Simply put, the Glycemic Index describes the speed at which the body breaks down food to form glucose, or energy,” he says. “The faster the food breaks down, the higher the G.I. rating.”

Gallop says low-G.I. foods break down more slowly and leave you feeling full and satisfied longer — so you’re not looking for that next snack. He recommends fruits, raw vegetables, whole-grain bread, low-fat dairy products (like yogurt) and nuts.

“Low-fat dairy has lots of vitamin D and calcium, which seniors need more of,” he says. “Nuts are terrific. They are low in saturated fats and high in protein. Just watch the quantities.” About 10 nuts is a serving.