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Experts say changes in eating habits as people enter adulthood can cause weight gain. Raimund Koch/Getty Images
  • Researchers report that the biggest weight gain in U.S. adults is happening in the mid-20s to mid-30s.
  • They say people in that age group tend to shift focus from physical fitness to other issues such as jobs, families, and finances.
  • Researchers also note that women tend to gain more weight during this time, in part because of weight gain during pregnancy.
  • Experts say people of all ages should eat a more healthy diet and be patient if they are trying to lose weight.

Step aside, “Freshman Fifteen,” there’s a new age-related weight gain in town.

Call it the “Trend up Twenties” or perhaps the “Thickening Thirties,” but researchers have found that the highest weight gain comes not in college or middle age, but in the early adult years.

A new study, published in the Journal of Obesity, is the first to hone in on how weight gain tracks throughout a person’s life.

Larry Tucker, PhD, the study’s lead author and a professor of exercise sciences at Brigham Young University in Utah, told Healthline what makes this research important is the fact that rather than look at obesity rates at a certain point in time, it dug into how obesity develops over years.

“We typically study obesity as an outcome,” he said, “and look at a point in time,”

But weight gain, he pointed out, “is a process. Most people see obesity in general as more common in middle age and older age. But that’s because weight gain is cumulative.”

The study used data from the National Health and Nutrition Examination Survey on 10-year weight change patterns of more than 13,800 adults in the United States.

Researchers say they found that the average respondent gained about 17 pounds from their mid-20s to mid-30s.

That average weight gain dropped to 14 pounds in their 40s, about 9 pounds in their 50s, and less than 5 pounds from the 50s on.

In addition, women gained nearly twice as much weight as men. Black women gained even more.

Tucker, who has studied obesity his entire career, thinks he knows why.

“In the early and mid-20s there is a lot of pressure in society to be lean,” he said. “As people are dating and making impressions in life and work, we tend to be ‘weight conscious.’”

As time goes on, Tucker said, people tend to shift to other focuses such as jobs, family life, and finances.

Dr. Mir Ali, a bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in California, told Healthline that while this study provides some new information, it also backs up what his facility has seen clinically for some time.

“As people marry, they tend to get more sedentary and less conscious of diet,” Ali said.

It’s also, Tucker said, an issue of the foods we choose and have easy access to.

“Food is, for many people, one of the few significant pleasures,” he said.

The food industry, he notes, “keeps getting better and better at enticing us, making it easy to access and easy to prepare” foods that aren’t necessarily healthy choices.

Women, Ali said, tend to be more socially impacted by weight and appearance at a younger age.

About 90 percent of the weight loss surgeries his clinic does, he said, are on women.

“They’re more conscious of (weight gain),” he said.

Women also bear children, which brings with it a unique weight challenge.

“The literature supports that having babies leads to weight gain,” Tucker said.

And while the weight can be lost, Tucker said, losing pounds gained during pregnancy “takes significant effort,” and weight can “stack up kid upon kid.”

What’s the solution?

Both experts say U.S. society needs to address the issue from an early age.

Those who may already be gaining weight early need to make changes slowly and steadily.

“We cannot ignore the young adults even though obesity manifests later in life,” Tucker said. “Our school systems need to advise and encourage healthful eating and living philosophy.”

Individually, both experts said, we can take steps to turn things around. Here are some suggestions.

Adapt how you eat

The majority of weight loss, Ali said, comes from changing to a healthier diet. Look to reduce sugars and carbohydrates and add more whole food and vegetables to your intake.

“It will force your body to burn fat,” Ali said.

Working on better food choices first will tee you up, Ali said, to have a more productive exercise result.

All notes, too, that you cannot turn this around with just exercise.

“The majority (of weight loss results) comes from food choices,” he said, “and then from exercise.”

And don’t deprive yourself too much.

“Find a way of eating that’s healthy, enjoyable and sustainable,” he said.

Regular aerobic/cardio activity

It doesn’t mean you need to do wind sprints or climb a mountain, Ali said.

Rather, do whatever makes you happy: Walking, swimming, cycling, hiking – anything that raises that heart rate.

Tucker suggests a minimum of 150 minutes a week. If you’re trying to lose weight, you should work your way up to 300 minutes a week.

“Consistency is more important than extreme,” Ali said. “Even just walking is good if you do it regularly.”

Be patient

If it takes 10 years to become obese, it’s not going to correct itself in 10 days,” Tucker said.