“It doesn’t affect us as much because of the way we shop,” says Art Shillito, who along with his wife, Janelle, forgo shopping lists and mostly buy marked-down items. The Burnt Hills, N.Y., couple say they’ve spent an average $364.74 a month this year to feed their family of 11, which is below last year’s monthly average of $500.

With high inflation costing many Americans more, a small but enthusiastic group of already-super-frugal people are taking their saving strategies further. Some of their tactics: checking wholesalers for sharply reduced “distressed” foods with damaged packaging; designating no-spend months when they abstain from buying nonessentials; and auditing one or two categories of spending to see where they can shave costs.

Extreme money-saving measures are gaining interest as more than 80% of American consumers say they plan to cut back spending by buying cheaper or fewer products, according to a May survey of 1,014 people by market research firm NPD Group…

“People find what we do interesting but when they find out how involved it is, they’re not interested,” says Mr. Shillito, 49. “They want a couple easy solutions.” Mr. Shillito recently repaired the roof on the family home himself, spending $1,065.34, considerably less than the $7,356.08 estimate received for someone else to do it.