SAN FRANCISCO — In recent years, millennials have been blamed for the downfall of canned tuna, mayonnaise, American cheese and ready-to-eat cereal. Another victim of the generation may be the traditional homecooked dinner.

Shifting demographics have upended the evening mealtime routine, said Dave Donnan, senior partner at A.T. Kearney.

Generations ago, he said, a family of four or five would gather around the dinner table and eat whatever dish mom prepared. Today, 62% of households are either single or couples, he said.

“That has changed the dynamic of how we make food," Mr. Donnan said during a Jan. 14 presentation at the Winter Fancy Food Show in San Francisco. "In addition it’s just not one meal anymore because even if I have more than one person at the table, somebody will be gluten-free, another will be a vegan, and then someone will be paleo, and someone is trying to be keto. Each one of those different menu options is causing more complexity to our meals.”

The rise of specialty diets emerged as a theme in several talks at the event. Sophie Egan, an author and freelance writer, described the perpetuation of a “very me-centric American food culture” that has fueled a fascination with functional ingredients and personalized nutrition.

“Personalized nutrition stands to further distance us from each other and the table,” she said during a Jan. 13 presentation at Winter Fancy Food.

Millennials and what Mintel refers to as the “iGeneration,” the cohort born between 1995 and 2007, have disrupted the institution of dieting, said David Lockwood, director of Mintel Consulting. In a survey, Generation X and baby boomer participants indicated they had tried approximately 3.5 different diets in the past year and 4.5 different diets over a lifetime, Mr. Lockwood said.

“Already, at their young age, millennials and iGens, the youngest groups, are dieting more frequently in their short lifetimes than older adults in their long lifetimes,” he said. “What you get is serial dieting. People who will go through Whole30, paleo, even keto now, and just try them over and over and over and keep doing it.

“That’s so important for food innovators … what that means is it’s changing almost everything about the way we’ve thought about and developed products for and marketing to diets. Younger generations don’t even stick with a diet long enough to see how it’s supposed to work.”

New products and services further enable an expectation of customization, Ms. Egan said. She said there are 87,000 possible beverage combinations at Starbucks.

“This has evolved to build-your-own fast-casual models where you are a participant in the meal making — you’re sort of the orchestra conductor, dialing your meal to your unique hedonic and health profile,” she said. “This stems from a much deeper undercurrent in our food culture, which has been described today as … this need for transparency. It’s a sense of, ‘It’s my right to know what’s in my food. It’s my right to know what I’m putting in my body.’”

Food service models are scrambling to keep pace. Raley’s, a regional supermarket chain, shifted its focus recently to broaden its assortment of prepared foods. Evelyn Miliate, corporate chef at Raley’s, said the retailer offers meals and mini meals, mix-and-match meal components and meal kits catering to different dietary preferences.

“What drives our growth is giving customers choices, whether it be dietary choices, sizes of meals that they eat, varieties, just the way you cook it,” Ms. Miliate said. “We don’t market it as lifestyle diets such as keto or paleo diets, but we certainly have (those trends) in mind while we’re developing our products.”

Meal kit company HelloFresh recently expanded its offerings to draw more consumers, said Matthew Fitzgerald, senior vice-president of brand marketing.

“The meal kit concept hasn’t been accessible for everybody, so we pioneered a multi-brand strategy,” he said. “We bought a company called Green Chef based in Boulder, Colo., that has specialty meal plans, especially keto and organic ingredients. We are seeing very strong demand for those types of diets.”

HelloFresh also added value meal kit brand Every Plate, with prices beginning at $4.99 per meal.

“We saw in our research many people across the country felt left out by this trend,” Mr. Fitzgerald said. “They just could not afford meals starting at $9.99 per person. Using our supply chain, technology, insights into how we design our recipes and how we can help the home cook, we were able to unlock a concept at a much more accessible price point, and it’s actually our fastest growing plan to date.”

Uber Eats, the food delivery service, also has evolved its model to tap into specific dietary needs, said Bowie Cheung, director of operations.

“From a food delivery app perspective, one way you go about doing that is introducing filters for your dietary restrictions or preferences, whatever it might be,” Mr. Cheung said.

Prepared foods, meal kits and restaurant delivery are capturing more growth as consumers increasingly seek convenient dinnertime solutions, Mr. Donnan said.

“In fact, 70% of consumers, according to a recent NPD survey, said they like to eat at home, but only 10% of consumers said they love to cook,” he said. “So, we’ve got this dichotomy between wanting to be home to eat but not wanting to cook.”