The research firm's 2011 report on diet foods said that sales values of low-fat, reduced-sugar and other similar foods and drinks will rise from around £5.42bn this year to £6.89bn in 2015.
But growth will be driven primarily by the increase in the price of commodities and raw materials, sparked by inflation not dropping particularly significantly between 2011 and 2015, Keynote said.
While the diet foods sector generally steers clear of sugar and uses alternatives as a way to reduce calories in its foods, the rising price of sugar is likely to impact the market, the report also suggested.
The use of artificial sweeteners in general food and drink products is likely to become a growing trend if the global price of sugar keeps rising; aspartame and sucralose are attractive alternatives to expensive sugar.
However, this could lead to demand increasing faster than supply, which would push prices up in the sectors of the diet foods market that use them.
The report also said that meal-replacement products have been falling out of vogue of late, owing to a surge in the popularity of low-calorie alternatives to traditional foodstuffs.
Rather than replacing food and meals with shakes or low-calorie protein or energy bars, consumers can eat “healthier” versions of the foods they enjoy, in moderation, and still achieve weight loss, it added.
The market for low-fat and reduced-sugar products increased very rapidly between 2006 and 2010, rising from £3.84bn in 2006 to £5.33bn in 2010, the report said.
However, the overwhelming trend in the diet foods sector is adopting a healthy approach to dieting, which involves becoming educated about one’s diet and adjusting consumption of various foods, Key Note said.
But low-fat, reduced-calorie, -sugar and -salt ranges are seeing a boom in innovation, with a huge number of large brands bringing out healthier alternatives to their products.
Dairy products are by far the largest sector in the diet foods market, valued at around £3.35bn in 2010. Most of this value is accounted for by semi-skimmed, skimmed and 1%-fat milk.
Other key categories include diet versions of cheeses, butters and spreads, chilled desserts, yoghurts and yoghurt drinks.
The next-largest category is low-fat and reduced-sugar bakery products, with the healthy ready meals (chilled and frozen) sector forming the third-largest segment of the total market.
Key Note also reported that exports of cakes and other bakery wares without sweetening matter were the UK’s most lucrative diet food export in 2010 — exports of these accounted for £90.6m, 38.6% of the total exports of diet foods.
The product the UK exported least in value terms was reduced-fat butters and spreads, exports of which were worth only £185,000 in 2010, accounting for just 0.1% of total diet food exports.
The diet product the UK imported the most of by value was cakes and other bakery wares without added sweetening matter. The UK imported £396.2m-worth of these products in 2010 (49.8% of total diet foods imports).
The lowest level of imports was accounted for by jams and marmalades, cooked preparations of citrus fruits, fruit jellies and fruit purées, with a sugar content exceeding 13% but not exceeding 30%; imports were worth £2.4m in 2010, or 0.3% of the total.