Not sleeping enough or getting a bad night's sleep over and over makes it hard to control your appetite. And that sets you up for all sorts of health problems, including obesity (肥胖), heart disease and high blood pressure.

The link between poor sleep and a greater body mass index (BMI) has been shown in study after study, but researchers typically relied on the memories of the participants to record how well they slept. Sleep apps on fitness trackers, smartphones and watches have changed all that. In a new study researchers tracked sleep quality for 120,000 people for up to two years.

The results showed sleep durations (持续时间) and patterns are highly variable between people. Despite that, the study found people with BMIs of 30 or above — which is considered obese by the US Centers for Disease Control and Prevention — had slightly shorter sleep durations and more variable sleep patterns.

It didn't take much less sleep to see the effect. People with BMIs over 30 only slept about 15 minutes less than those less weighty people.

There were some limitations to the study, naps (午睡) were not included, other health conditions could not be factored in, and people who use wearable tracking devices are typically younger, healthier and from a higher economic status than those who do not wear trackers.

"These are quite pricey devices, and they are not approved by the US Food and Drug Administration. The results would need to be validated (确认) by the appropriate FDA-approved devices, and because the study is likely on younger people who are more economically well off, it needs further study whether that really applies to older folks with poor sleep." said Dasgupta, the associate program director.

However, Dasgupta added, a major plus for the study is that it did monitor people for over two years, and the results corroborated previous research and were "not surprising."

While we cannot determine the direction of association from our study result, these findings provide further support to the idea that sleep patterns are associated with weight management and overall health.