Uh-oh.

When I was in D.C. last month visiting family, I went on an ice-cream binge. (Hey, it happens, even to health reporters.) And every day, it seemed, I came up with a creative excuse (mostly having to do with the horrific humidity) for not exercising.

Needless to say, I put on a couple of extra pounds by the time I returned home. With a bit of effort, I figure I’ll soon be rid of them.

Or could that be wishful thinking?

A Swedish study published earlier this week suggests that just a few weeks of overeating and under-exercising can affect our physiology in ways that make it very difficult to shed all the extra poundage we gained — even after we’ve returned to our non-slothful eating and exercising habits.

Like I said, uh-oh.

For this study, which appears in the current issue of Nutrition & Metabolism, researchers recruited 18 normal-weight (based on BMI) medical students. They included 12 men and six women, and their mean age was 26 years. Amazingly, all agreed to follow the study’s month-long diet-and-exercise regime, even though they were told it might increase their body weight by 5 to 15 percent.

In fact, the regime was designed to bulk them up. The students were told to restrict their physical activity to no more than the 5,000 steps per day — the upper limit for what’s considered a sedentary lifestyle. (The students were given pedometers before the study began so they’d get a sense for how much physical activity is involved in 5,000 steps.) They were also instructed to double their daily calorie intake. To accomplish this, the researchers recommended at least two fast-food meals per day. (The students actually ended up increasing their calories by an average of 70 percent.)

Eighteen other students were recruited for a control group. They were asked to not change their eating or exercising habits for one month.

At the end of the month, the students who had upped their eating and lowered their physical activity had gained an average of 14 pounds. The gains were in both their body fat (measured by Dual energy x-ray absorptiometry) and their fat-free body mass.

Over the next year, the students lost most of the gained weight (an average of 10 pounds each), but they still retained more body fat mass (an average of 3 pounds) than they had before they had entered the study.  And at two-and-a-half years, the body fat mass gains were even greater — an average of 6.8 pounds. They had, though, lost all their extra fat-free body mass. No similar weight change was seen in the control group.

These findings suggest, said the study’s authors, that even short-term changes in eating and exercising behaviors may have prolonged effects on our health.

The study has its limitations, of course. For example (and as the Swedish researchers acknowledge), the students volunteered for the intervention group. It may be, therefore, that they were less worried than the control group about gaining weight — an attitude that might explain their extra poundage over the two-and-a-half years and that might have biased the study’s results.

Still, no more ice cream binges for me.

FYI: One of the interesting background details in the study was the difference in the amount of weight typically gained by Swedes and Americans as they age. In Sweden, the 10-year weight gain for the average adult (aged 25 to 64) is 8.4 pounds. In the U.S., it’s 20 pounds.