A study into 30 of the most popular diet apps, which can be downloaded on to smartphones and tablets, found most included few or no behavioural weight-loss strategies. Researchers in America also discovered that free apps were just as useful as premium downloads.
Weight loss expert Sherry Pagoto, of the University of Massachusetts Medical School, said: "Apps do include evidence-based behavioural strategies, but only a narrow range.
"Strategies that often were missing are ones that help patients with adherence and motivation."
Behavioural weight-loss strategies that are evidence-based - scientifically researched and found to be effective - include stimulus willpower control, problem solving, stress reduction and relapse prevention.
Researchers were also interested in determining whether apps incorporate features to enhance behavioural strategies. Enhancements include barcode scanners that can be used to get nutritional information, social networks where users can encourage and support each other, email and text reminders, and calendars for scheduling exercise and tracking food intake.
Martyn Landi, reviews editor with British-based Apps magazine, said weight-loss software should not be used in isolation. "A little bit of common sense is needed with these apps," he said.