If you only have a limited amount of time to devote to being physically active, choose an aerobic activity such as cycling or brisk walking. The reward is better health. (Jonathan Hayward/Canadian Press)

The fittest Canadian adults are the healthiest in many ways, Statistics Canada has found amid declining physical activity levels and expanding waistlines.

In a report released Wednesday, researchers analyzed data from more than 7,600 respondents to the Canadian Health Measures Survey with an average age of 40 who did fitness tests, answered questions about their health and had their blood pressure, cholesterol and blood sugar levels checked.

"The fittest Canadian adults are the healthiest," said report author Jonathon Fowles, director of the Centre of Lifestyle Studies at Acadia University in Wolfville, N.S.

"A lot of people say that they're active or not active but when you actually measure fitness, it's not like you can fake that."

Against the backdrop of yesterday’s findings that physical fitness levels of Canadian kids are near the back of the pack internationally, Statistics Canada has tracked the plummeting of physical fitness levels, which are down 15 to 25 per cent over 30 years at the same time sedentary behaviour like sitting in a car has increased.

"The bottom line is that being aerobically fit was the No. 1 very strong relationship" to health, Fowles said. "If you only have a limited amount of time to devote to being physically active, well then, get out there and do some aerobic activity like brisk walking, cycling or swimming."

Being muscularly fit was the next most important type of fitness.

In the study, those who scored in the "excellent" category of fitness had greater health outcomes and said they were in better health than those in the "needs improvement" fitness category.

For doctors, nurses and fitness professionals, the findings support the need to take out a tape measure and check waist circumference, because abdominal obesity so strongly relates to overall health.

The findings also offered reminders to trainers about contextualizing fitness test results to the individual’s health risks, he said.

With files from CBC's Amina Zafar