A new study adds to evidence that obesity is becoming more common in young children in America.

The study appeared in the medical publication Pediatrics.

The findings are similar to other national data, which suggests around 2.5 percent of all preschool-aged children were severely obese during the same period.

One of the study's writers, Heidi Blanck of the U.S. Centers for Disease Control and Prevention, said "We were doing well and now we see this upward trend....We are dismayed at seeing these findings."

Dismayed is a term that means very worried or disappointed.

The study looked at children ages 2 to 4 who took part in the Women, Infants and Children (WIC) program. The program gives healthy foods and other services to preschool-aged children in low-income families. The children were weighed and measured.

The researchers found that 2.1 percent of kids in the program were severely obese in 2010. Six years later, the rate had dropped to 1.8 percent. But by 2020, it was 2 percent. That amounts to about 33,000 of more than 1.6 million kids in the WIC program.

The study showed major increases in 20 states. California's was the highest at 2.8 percent. There also were large increases in some racial and ethnic groups. The highest rate, about 2.8 percent, was among Hispanic children.

Experts say severe obesity at a very early age is nearly irreversible – meaning the damage is nearly impossible to undo.

Severe obesity is strongly linked with health problems and an early death.

It is not clear why the increase occurred, Blanck said.

When WIC obesity rates dropped, some experts suggested 2009 policy changes might be responsible. Those changes took out juice from infant food packages, provided less saturated fat, and tried to make it easier for people to buy fruits and vegetables.

The package has not changed. But "the daily hardships that families living in poverty are facing may be harder today than they were 10 years ago, and the slight increases in the WIC package just weren't enough," said Dr. Sarah Armstrong, a Duke University childhood obesity researcher.

The researchers faced difficulties. The number of kids in WIC declined in the past ten years. And the study included 2020, the year the COVID-19 pandemic hit. At the time, fewer parents brought their children in to see doctors. That reduced the amount of complete information available.

Despite its limitations, it was a "very well done study," said Deanna Hoelscher, a childhood obesity researcher at the UTHealth Houston School of Public Health. She added, "It gives you a hint of what's going on."

What has happened since 2020 is not yet known. Some small studies have suggested an increase in childhood obesity — especially during the pandemic. During the pandemic, kids were kept home from schools. Their eating and bedtime schedules were changed and physical activity decreased.

"We are thinking it's going to get worse," Hoelscher said.

研究发现，肥胖在美国年幼儿童中变得越来越普遍，这一发现与其他国家的数据相似，表明在同一时期，大约有2.5%的学龄前儿童出现了严重肥胖。

研究的作者之一海蒂·布兰克来自美国疾病控制和预防中心，她表示：“我们以前做得很好，但现在我们看到了这种上升的趋势…我们对这些发现感到沮丧。”“沮丧”是一个意味着非常担忧或失望的词。

该研究着眼于参与妇女、婴儿和儿童营养补助计划(WIC)的 2 到 4 岁儿童。该计划为低收入家庭的学龄前儿童提供健康食品和其他服务。研究人员对这些儿童进行了体重和身高测量。

研究发现，2010 年该计划中有 2.1% 的儿童出现了严重肥胖。六年后，这一比例下降至 1.8%，但到了 2020 年，又上升到了 2%。这意味着在 WIC 计划中超过 160 万儿童中约有 33,000 名严重肥胖。

该研究显示，在 20 个州出现了严重增加。加利福尼亚州的情况最为严重，严重肥胖率达到了 2.8%。某些种族和民族群体的严重肥胖率也出现了大幅增长，其中西班牙裔儿童的严重肥胖率最高，约为 2.8%。

专家表示，非常早期的严重肥胖几乎是不可逆转的，即损害几乎无法弥补。严重肥胖与健康问题和早逝密切相关。

目前还不清楚为什么肥胖率会增加。当 WIC 肥胖率下降时，一些专家认为 2009 年的政策变化可能起到了作用。那些变化取消了婴儿食品包装中的果汁，提供了更少的饱和脂肪，并试图让人们更容易购买水果和蔬菜。

研究人员面临了困难。过去十年里，WIC 的儿童数量有所下降。而且该研究包括了 2020 年，这一年正值 COVID-19 大流行。当时，较少的家长带孩子去看医生，这减少了可用的完整信息量。

尽管存在局限性，但得到了“非常出色的研究”的评价。一些小型研究表明，在疫情期间儿童肥胖情况有所加剧。

总之，这项研究揭示了美国年幼儿童肥胖问题日益严重的趋势，对社会和健康带来了挑战，需要引起重视。