Over and over, the people who study healthy living have found that will power plays a far smaller role than we’d like to give it credit. Reaching for the last cookie isn’t so much an active choice as one of habit, especially if we just scarfed down five others before it. This can be a scary realization. After all, if we’re not in control of our own health, then who is?

Emerging evidence would suggest that large-scale policy decisions may end up affecting the health of a population more than the individual choices people make. The latest piece of research was published in the journal Obesity Reviews, and it found through a systematic analysis of prior studies that fitter, cleaner-eating populations end up making very few of the healthy living choices for themselves.

What did help people to be more active were public amenities such as bike lanes, trails, playgrounds, and light rail systems. Stephanie Mayne, lead author of the study and researcher at the Children’s Hospital in Philadelphia, says the findings give some hope to the idea that people want to be more active, if only their neighborhoods were built to accommodate them. “It just seems to let people integrate that physical activity into their day more easily,” Mayne said of the amenities.

The more integration the better, it would seem. Even with increasing awareness about America’s obesity epidemic, trends haven’t shown any signs of stopping. More than a third of the country is obese and more than two-thirds are overweight. Worse, evidence suggests that kids today are, on the whole, less fit than their parents were 30 years ago.

Even without hard proof, some populations have already adopted the very measures Mayne and her colleagues have come to endorse. In Boulder, Colo., for example, people can ride their bikes from one end of the city to the other and never cross the street, allaying fears people may have of dealing with bustling traffic. In Copenhagen, Denmark, a country renowned for its cycling culture, at least 50 percent of people commute to work by bike. Many credit the country’s easy-access bike sharing program as a driver of its fit philosophy.

Not all public policy initiatives pay off. According to Mayne, changes to nutrition labels and supermarkets built in underserved areas didn’t get people eating any healthier. This has been demonstrated before. In 2013, the Centers for Disease Control and Prevention found prominently displayed calorie counts didn’t affect people’s decision to indulge in unhealthy food. And earlier this February, researchers from NYU found childhood obesity continued to flourish despite government programs to keep grocery stores stocked with fruits and vegetables. People may want to be healthier, but it takes a special kind of nudge to get them there.

Mayne concedes the recent review can’t serve as a gatekeeper for all policy decisions. For example, many of the studies she and her team analyzed failed to track whether people actually got any healthier from the change to their environment. Instead what they got were data simply on people using more bike paths and trails, not necessarily whether those lifestyle shifts made a difference. “It’s promising that they seem to be using these amenities,” she said. “But there definitely to be more studies looking at the effect not only on BMI [body mass index] and weight, but also on overall diet and physical activity.”

Large-scale policies for promoting public health aren’t just effective for encouraging a culture of fitness in people who have no current desire to live healthy — though, that certainly has been observed. They also seem to help sway people who are on the fence. They are the people who, year after year, make the resolution to lose 15 pounds and eat right, but because of the hassle of rush hour and tending to housework, lose sight of their goals.

An environment that enables people to fold in a healthier lifestyle into their normal routine lets people live longer without having to rearrange their lives.

Source: Mayne S, Auchincloss H, Michael Y. Impact of policy and built environment changes on obesity-related outcomes: a systematic review of naturally occurring experiments. Obesity Reviews. 2015.