Big-box retailers like Kroger and Walmart have used their extensive nationwide operations to negotiate better deals with suppliers, which allowed them to keep prices substantially lower than competition and lure more people.

Kroger has also profited from shoppers - including higher-income consumers looking for more economical options amid persistent inflation - switching to its store-label brands from pricier national brands.

Shares of Cincinnati, Ohio-based company, which is set to buy smaller rival Albertsons in a $25 billion deal, were flat in premarket trade after the company reaffirmed its annual forecasts.

The company said same-store sales, excluding fuel, rose 3.5% in the first quarter ended May 20, compared with analysts' average estimate of a 3.27% increase, according to Refinitiv IBES data.

Excluding special items, Kroger earned $1.51 per share, beating estimates of $1.46 per share.