A tie-up with US website eDiets.com will allow Tesco to offer a 'seamless' diet programme, from choosing the plan to generating an automatic shopping list of the necessary foods, which can then be delivered to customers' homes.
Although the diets available include low-calorie and low-carb plans such as Atkins, the supermarket is also targeting people with restricted eating requirements, such as lactose intolerance, who would usually have to check ingredient contents on every product.
It is the latest initiative in Tesco's 'Healthy Living' strategy, following the introduction of a glycemic index rating on food labels in June, as well as the trial of 'traffic light' labelling to indicate foods that are high in fat, sugar and salt.
Tesco.com chief executive Laura Wade-Gery said the move into online dieting was a natural progression for its online shopping service, which now has 3m registered users and sales of more than £500m, making it the world's biggest online grocer.
The deal means Tesco.com controls all licensing for eDiets in the UK and Ireland, the second-biggest diet market in the world after the US.
Tesco claims that converting a diet plan into a food delivery with one click will be a world first.
The subscription service, which will cost £12.99 a month, is the third to be launched by Tesco in as many months, following online DVD rentals, through Video Island, and legal services last month.