However, although sales rose at both groups, the supermarket chains' market shares were lower than this time previous year, falling by 0.3 and 0.1 percentage points respectively.
"Given the competitive landscape in United Kingdom grocery retail, profitable growth and expansion opportunities are limited, so reducing resources makes sense especially when there are other geographies and channels" with more opportunity for growth, said Moody's Lead Retail Analyst Charlie O'Shea.
Latest figures show that Tesco has a 27.6% market share, while Sainsbury's has 15.8% and Asda has 15.6%.
Sainsbury's is valued at around £5.9 billion.
The merger, between the UK's number two and three supermarkets, was agreed upon by the two companies but awaits approval from the Competition and Markets Authority (CMA) in order to be finalised.
The chief executive of United Kingdom supermarket giant Sainsbury's has been filmed singing We're in the Money, just hours after announcing the company would buy rival Asda, boosting their value by more than $1 billion.
In Britain's grocery market, discounters have taken market share from traditional chains such as Sainsbury's and Tesco.
"An action plan has been put in place following the announcement of the merger of Sainsbury's and Asda".
The two have different cultures and appeal to different customers, with London-based Sainsbury's strong in own-brand products, and Asda, headquartered in Leeds, northern England, focused on price.
Bernstein analyst Bruno Monteyne pointed to the execution risks, noting Morrisons-Safeway lost 28% of their sales through a combination of store sales, integration problems and culture clash when they merged.
It will aim to generate £500 million in cost savings but Sainsbury's insisted there are no planned store closures as part of the merger, with both brands to operate side by side.
After a two-year lock-up period, Walmart is allowed to reduce its stake in the combined group to 29.9 percent, and after four years could exit completely.