I once received a lot of blowback for an Upshot article in which I showed (with evidence) that exercise is not the key to weight loss. Diet is. Many, many readers cannot wrap their head around the notion that adding physical activity, and therefore burning more calories, doesn't necessarily translate into results on the scale.

Well, here we go again because some of those folks also believe that fitness devices - Fitbit, Vivosmart, Apple Watch - must be helpful in losing weight. Unfortunately, evidence doesn't support this belief either.

Wearable technology for fitness? The evidence isn't there. Credit:iStock

For some time, people have been trying to prove devices like these succeed in promoting weight loss. In 2011, a study compared four groups getting a mixture of behavioral weight loss programs and use of an armband that measured activity and energy expenditure. All the intervention groups lost weight, but those with behavioral programs and technology lost the most. The sample size of each group (fewer than 50) and the large dropout rate of the study should temper enthusiasm, though. The sample was also mostly female, and more than three-quarters of them had university degrees, so the results may not be entirely generalisable.

In 2015, another study, the PACE-Lift trial, was also inconclusive. Researchers randomly assigned 250 people ages 60 to 75 to one of two groups. The first group received four physical activity consultations from primary care nurses over three months; a pedometer; and a physical activity diary. The other received "usual care." All patients were given accelerometers to measure their activity, although only the control group saw the results. One year later, those in the pedometer group were taking an average of about 600 more steps per day and had about 40 more minutes of activity a week.