Although the public health community has been trying to address the childhood obesity epidemic for years, progress has been disappointing. Often, governments or schools will make a single policy change — more fruit in school lunches, no soda machines in parks — only to find no effect.

Matthew W. Gillman has some ideas why. He is a pediatrician, a former professor of nutrition at the Harvard T.H. Chan School of Public Health and is now the director of a seven-year, $1.15 billion study by the National Institutes of Health — a study named ECHO, for Environmental Influences on Child Health Outcomes. Research that Gillman and others have conducted over the past 15 years indicates that the origins of obesity lie as much in early childhood — even prenatally and intergenerationally — as it does in an individual’s current behavior. He spoke with The Post recently about what science can tell us about kids and obesity.

Q: Recent research seems to suggest that whether someone is obese may be determined even before they are born.

Matthew W. Gillman is the director of a seven-year study on child health at the National Institutes of Health. (Courtesy of Harvard Medical School)

A: What happens at the earliest stages of human development — even before birth — has long-lasting, sometimes lifelong, sometimes irreversible consequences.

There are a number of things, prenatally and early postnatally, that predict obesity, and more in combination than they do singly. We think about the weight of the mom coming into pregnancy, about how much weight the mother gains during pregnancy, whether or not she develops gestational diabetes. We just published a paper in Pediatrics that showed that moms who consume larger amounts of sugar-sweetened beverages during the second trimester have kids with higher [body mass index, or BMI] at school age. Rapid weight gain in the first six months of life, early introduction of solid foods, the less sleep you get as an infant — all of these make it more likely you will be obese as a child.

Q: Could the same thing be causing obesity and other health problems in kids?

A: That’s an open question. For instance, obesity is related to asthma. It could be that one environmental factor is causing asthma and another is causing obesity, and certain kids are susceptible to both. It could be that some of the same pathways, like inflammatory pathways, lead to both. It’s also true that obesity causes asthma, probably both from inflammatory factors and that you’re just squeezing the lungs. And it may also be that asthma causes obesity because kids with asthma get less physical activity. So you’ve got common underpinnings, you’ve got separate underpinnings, and you’ve got one causing the other. And that’s another thing we’re trying to do in ECHO is tease apart some of these complexities. That can also tell you the best time and maybe the best ways to intervene, or at least to test interventions.

Q: What do we know about the effect on a fetus of developing in a low-nutrition environment, or a high-stress environment, and how that might be related to later obesity?

A: There are some great animal models — baboons and rats — but only hints in humans. Kids born at lower birth weights because of low fetal growth who then gain more weight in childhood have worse cardiovascular outcomes. While they don’t have higher BMI than those born larger, they may have more fat in the wrong places. Maternal smoking is related to both lower fetal growth and to obesity in childhood.

Q: So how does obesity become an intergenerational issue?

A: Sometimes [when we talk about intergenerational effects] we mean mother-to-child, but oftentimes we mean mother to a child who grows up to be a mother and passes her mother’s influences to her own child, the grandchild. If a woman comes into pregnancy at a high weight, she may develop gestational diabetes, and if she does, her offspring are more likely to be obese. If that’s a girl, then she’s more likely to be overweight if she gets pregnant. So you get into these intergenerational vicious cycles. Interventions during school age and adolescence could interrupt that by allowing women to come into pregnancy at closer to an ideal weight.

Q: How do you get kids and adolescents to lose weight when their prenatal or early life experience is what’s making them obese?

A: That’s a really, really good question. Once obesity is present, it resists treatment. It’s also behavioral: We have entrenched behaviors and they’re hard to break, and we have cultural things and environmental things like food systems and physical activity systems that tend to resist weight loss. So we think early prevention is really the key. Early life factors set people on a more unhealthful trajectory; then, because of all these resistance factors, it’s hard to turn around.

Q: What has been shown to work?

A: On an individual basis, working with families and working directly with kids — especially if there’s a multidisciplinary approach — can work. There are also whole-community interventions that show promise. Shape Up Somerville, a program results of which were published close to 10 years ago, was changing the large- and medium-scale environment in Somerville, Mass., for school-age kids. They lost more relative weight than kids did in neighboring communities. That was clearly multifactorial. The health-care system, the schools, community groups, local government — each one did something a little bit different: Schools changed what they served. The local government made it easier to get physical activity.

In each age group, you can think about different sectors that can be involved. I think that’s the way of the future. A project I was working on before I came to [the National Institutes of Health] was using computational approaches to try to figure out which communities might be ready and which kind of interventions to implement in different communities.

Q: So even when kids are predisposed to obesity, there’s hope?

A: Sometimes we look for the magic bullet. We say, “This is the thing with obesity, so we’re going to do away with it.” There’s not one thing: This obesity epidemic has been a long time coming, and it’s multifactorial. It involves everything from macro policy down to family and individual behaviors, and biology. The thought with these community interventions as well as some of the more individual interventions is you have an attack on multiple fronts.