The Lancet has described physical inactivity as pandemic. How serious is the situation?
It's certainly an under-recognised problem. One in three adults, globally, does not do enough physical activity - the minimum recommendation is 150 minutes a week of moderate exercise. It varies, with particular concern in emerging economies and high-income countries - only about 40 per cent are active enough in Australia and the US.
How bad is it in Scotland?
Scotland has 39 per cent being active, and inequalities within that - you're more likely to be active if you are male and of higher income and higher education.
Even if you're doing the recommended 30 minutes a day, isn't it dangerous to sit around the rest of the time?
Emerging evidence shows very strongly that there are indeed risks to sitting down too long. This is the difference between people who sit for seven hours at work, with little movement, and those who break that with short spells of walking and standing.
How long should we be sitting at most?
The science hasn't fine-tuned it to know where the risk is, but many of us know intuitively that when you sit too long the body and brain get sluggish. We're recommending breaks every hour, even just for five minutes. You can walk down the corridor rather than send an email, use the stairs rather than the lift, stand up when the phone rings, hold meetings standing rather than sitting. And in meetings we encourage a stretch break.
You've cited one CEO's unusual approach
Yes - George Halvorson of Kaiser Permanente has two treadmills in his office, linked up to computers, so not only can he have a walk at work but he can invite people to walk with him.
Scottish schools have a two-hour physical activity target. How much should pupils do at school?
The guidelines state children should accumulate an hour of activity every day overall - that's a minimum. We want to see a mandated number of classes. But around the world we're also seeing smaller playgrounds and the loss of playing fields and after-school activities. You shouldn't look at the curriculum in isolation.
What is the most crucial thing schools can do to raise physical activity levels?
Encourage walking and cycling. And, if I can say a second thing, teachers and heads should be role models for physical activity.
You spoke at the recent launch of the Physical Activity for Health Research Centre at the University of Edinburgh. How significant is this centre?
Developing the evidence base and using it to inform initiatives underway and planned for in Scotland is essential. The centre's research will be very important in Scotland and internationally.
What has struck you most during your visit to Scotland?
The progress made, particularly at high levels of government and leadership - support and recognition has increased since my last visit a couple of years ago. There is clear intent to address this problem.
We're in a time of technological innovation, widely viewed as a force for good - but you see another side to the story, don't you?
Across our daily lifestyle, things have been removed. Everything is digital, requiring us to do less physical movement, less incidental activity that made up a large amount of our energy expenditure. There is less priority on ways to be active - buildings are designed to put staircases towards the back, in favour of banks of elevators. It's a great pleasure to see the prominence of stairs in the Scottish Parliament.
You believe strongly in interventionist measures, such as smoking bans. If you could enact one law, what would it be?
Planning and community design should put cycling first - it would lead to a cascade of benefit, in both the transportation system and the design of more welcoming communities.
What's the best place you've seen for that?
Copenhagen, in how they turned a car-dominated city of the 1960s and 1970s into a world-leading cycling community.
You believe targets are crucial. Why?
What gets measured gets done. We need to monitor levels of physical activity, and I would encourage Scotland to measure at the level of local government.
Why is Canada's ParticipACTION programme significant?
It's one of a handful of examples of sustained action to increase physical activity. ParticipACTION, over 30 years, was an exemplar of how we could tackle physical inactivity. Unfortunately, it also shows that when we stop promoting physical activity, levels will plateau and even reverse.
So the lesson is never ease off at national level?
It will be a continual agenda item to promote physical activity. Particularly with children.
Reducing smoking has taken decades. Can physical inactivity be turned around more quickly?
I'm an optimist. We have a strong evidence base to guide action; with political and community engagement, we should be able to make a stronger impact, more quickly than with tobacco.
Born: California, 1965
Education: Kneller Girls' School, Middlesex; Exeter University, BEd physical education; sports science master's, Loughborough University
Career: Current roles include: director of Centre for Built Environment and Health, University of Western Australia; chair of Global Advocacy for Physical Activity Council; visiting professor at Loughborough and Cambridge universities; adviser to the World Health Organisation.