Among Americans and Europeans, overweight and obesity are endemic. Excess weight is also a primary or contributing cause and a significant risk factor for many chronic diseases, including diabetes, heart disease, stroke, several cancers, liver and kidney diseases, respiratory and musculoskeletal disorders, and mental health problems.

That being said, one can read any amount of advice we can make time for, concerning dieting or exercise. But a harsh reality persists: Fat cells (adipocytes) are not removed from the body through dietary changes alone. When you lose weight via diet and exercise, the fat cells shrink in size as their stored triglycerides are used for energy, but they remain present in the body.

Once you put on weight, your fat cells will lie in wait for the slightest slip on your part, to expand again — even at the expense of muscle building in a spa or gymnasium, or in daily exercise (jogging, running, aerobic workouts). And you will have food cravings for the rest of your life!

An average size (three-inch diameter) chocolate chip cookie will contain about 180 to 200 calories. After you put this delicious snack in your mouth, it will take serious effort to get it off your hips. For an old man like me (81 years) who has put on weight steadily through 45 years of marriage to an excellent cook who has the personal metabolism of a blast furnace, this is a catastrophe in the making. To burn off that cookie, I would have to be prepared to jog at least two miles at a moderate pace — shin splints and all.

Somehow, I don’t think that is going to happen.

If you value the lives and health of your kids, then two of the first habits that you must create in them are healthy eating and exercise. For a male who is six feet tall and who wants to avoid weight gain despite a sedentary lifestyle, your maximum input should be on the order of 2400 calories (ten chocolate chip cookies OR (not plus) three low-salt/low-sugar meals with a balance of protein, vegetables, and dietary fiber. Computer time and social media involvement must be reduced, and nightly sleep time must be adequate, particularly for adolescents.

For your generation and mine, this battle may already be lost. But for our kids, the cost of freedom (from health problems) will be constant vigilance.

The time to start is now.

Richard A. Lawhern is a patient advocate.