LONDON, Aug 13 (Reuters) - Ice cream companies may be enjoying a summer sales boost from soaring temperatures, but behind the scenes they are preparing for a future where consumers want fewer reasons to feel guilty about treating themselves.

The rise of appetite-suppressing GLP-1 drugs, demand for healthier foods and growing ingredient scrutiny are pushing manufacturers to reduce portion sizes, increase protein content in their recipes and clean up ingredients lists.

U.S. ice cream sales volumes fell 1.5% year-on-year through June 13, according to NielsenIQ, while Boston Consulting Group research shows GLP-1 users cut frozen treat consumption by at least 10%.

Yet manufacturers see little sign that consumers are abandoning ice cream altogether. Instead, ice cream makers are betting that shoppers will continue to indulge, provided treats come with fewer calories, more protein and simpler ingredient lists.

"We still want to indulge, but do it with a little bit of a halo of a wellness play," Lisa Vortsman, U.S. chief marketing and innovation officer at The Magnum Ice Cream Company, told Reuters.

Ferrero-owned Blue Bunny, for example, says demand has been strong for its 150-calorie Mini Swirls and it is reformulating recipes to remove ingredients such as high-fructose corn syrup and artificial colours and flavours.

"We know that there are certain ingredients that they don't want to see in their products as much anymore," said Andrew Mondzelewski, senior director for brand marketing at Blue Bunny.

The shift reflects a broader challenge facing the industry as changing eating habits reshape what consumers expect from indulgent foods.

REDEFINING INDULGENCE 

The Magnum Ice Cream Company, which owns brands including Magnum and Ben & Jerry's, has accelerated its focus on wellness-oriented offerings, citing strong growth in frozen Greek yoghurt brand Yasso.

Yasso has delivered average annual growth of around 20% over the past five years, while the group's other brands like Breyers CarbSmart and Popsicle Sugar-Free are particularly popular with GLP-1 consumers, Vortsman said. 

Vortsman said consumers were increasingly looking for products that combined indulgence with attributes such as higher protein, lower calories and more controlled portions. Magnum's brands make up a 26% share of the $2.2 billion U.S. wellness and functional ice cream segment.

"We are accelerating our wellness innovation funnel disproportionately faster than we have in the past," she said. 

Around 16 million Americans are taking GLP-1 medicines, according to Boston Consulting Group, with the number expected to climb significantly by the end of the decade. Food companies from Nestle to Conagra have been reformulating products as consumers seek more protein, fibre and nutritional benefits.

The challenge for ice cream makers is preserving ice cream's appeal as an indulgence while adapting to shoppers who increasingly weigh nutritional value alongside taste.

Ferrero's Halo Top brand, which aims to offer the same ice cream experience with half the calories of leading competitors, says it has delivered double-digit percentage sales growth over the last two years, compared with around 2.5% for the wider market, according to Circana, a Chicago-based market research firm.

Rather than shrink its serving size, Halo Top said in emailed comments that it prefers to pair "craveable flavours with a good source of protein and fewer calories than traditional ice cream". 

"Consumers have stopped giving indulgence a free pass," said NielsenIQ's Vice President of Food Thought Leadership Chris Costagli.

Dollar sales in the U.S. ice cream market rose about 2.8% over the past year, according to Circana. But NielsenIQ data showed super-premium products were the only segment to post volume growth.

The wellness trend is not confined to the United States, raising questions about how ice cream brands stay relevant as eating habits evolve globally.

Glacier, one of Europe's largest private-label producers, says demand is growing for smaller portions, premium products and lower-calorie ice lollies that fit broader health and wellness goals.

"If you are on GLP-1, if you're going to have a treat, you want it to be a really brilliant thing," said Glacier executive director Matt Frost. "The thing that we will be absolutely obsessed about is taste and repeat purchase because there's no point in nudging customers into better-for-you foods if they feel they're compromising on taste because they'll stop."