J. Schlotman
Analyst · Guggenheim Securities
Thanks, Rodney, and good morning, everyone. Like Rodney said, we were glad to see the better results compared to the fourth quarter for identical food store sales, and for the second quarter to date, our ID sales are positive.
Tonnage continued to be positive during the first quarter. We continue to focus on the areas of highest growth like natural and organic products as well as areas where we are serving -- saving customers time such as ready-to-eat and ready-to-eat meal solutions. Visits per household were flat in the first quarter. Basket size and price per unit were down, but those were offset by household growth. Loyal households grew 3.2% compared to last year's first quarter and our loyal households had positive ID sales growth in the first quarter.
In the first quarter, our gross margin was down, operating costs were up and FIFO operating profit was down. While this is not representative of our typical expectations, it is important to keep in mind that we're making very deliberate and targeted investments in line with our Customer 1st Strategy. As Rodney outlined earlier, we have made conscious decisions to increase starting wages in certain markets to improve associate engagement and retention that will create a better experience for our customers.
We continue to invest and grow our digital business. Our digital revenue more than doubled in the first quarter compared to last year. This includes revenue from ClickList, Harris Teeter's ExpressLane and Vitacost.com.
As we continue to invest in price, we also remind you, Kroger's investment in price can be seen very clearly if you look at gross margins in the early 2000s compared to today. Kroger has invested more than $3.8 billion to lower prices for our customers over that time period. We have no intention of giving up the momentum we've gained on low prices. These investments enable us to connect with our customers in a deeper way and increase our market share over time.
We are pleased that Kroger's market share, as traditionally calculated, was up in the first quarter. That said, we recognize there is no perfect metric for capturing market share. We are doing a lot of work to better define or perhaps redefine the market as a share of stomach rather than share among traditional grocery stores. We see food as a massive $1.5 trillion market and we have a substantial growth opportunity in that market. I also want to stress that we're committed to lowering costs as a rate of sales. Many of the things we are doing to pull costs out of the business today set us up for savings in the future. We will only further intensify our process improvement efforts.
Now for an update on retail fuel. In the first quarter, our cents per gallon fuel margin was approximately $0.171 compared to $0.143 in the same quarter last year. The average retail price of fuel was $2.28 versus $1.92 in the same quarter last year. Our net total debt-to-adjusted EBITDA ratio increased to 2.33x compared to 2.12x during the same period last year. This resolve (sic) [ result ] is due to the merger with ModernHEALTH and the repurchase of shares. Over the last 4 quarters, Kroger has used free cash flow to repurchase $1.5 billion in common shares, paid $438 million in dividends, invest $3.4 billion in capital and merged with ModernHEALTH for approximately $390 million. The flexibility to return value to shareholders is a core strength of our financial strategy. We are committed to balancing the use of cash to maintain our current investment-grade rating.
Return on invested capital for the first quarter on a rolling 4-quarters basis was 12.75%. On the labor relations front, we are currently negotiating agreements with the UFCW for store associates in Atlanta, Dallas and our Food 4 Less warehouse stores in Southern California. Our objective in every negotiation is to find a fair and reasonable balance between competitive cost and compensation packages that provide solid wages, good quality affordable health care and retirement benefits for our associates. Kroger's financial results continue to be pressured by rising health care and pension costs, which some of our competitors don't face. Kroger continues to communicate with our local unions, which represent many of our associates, the importance of growing Kroger's business and profitability, which will help us create more jobs, incur opportunities and enhance job security for our associates.
Turning now to our guidance for fiscal 2017. We have previously indicated that the environment during the first half of this year would be similar to the back half of 2016, and that is what we are seeing. As Rodney said, there is a lot of change in the retail food industry. That, coupled with the transition from deflation to inflation, creates a challenging operating environment. The deflationary environment was less severe in the first quarter compared to the fourth quarter, coming in at 20 basis points deflationary without fuel. Grocery was essentially flat during the quarter, but had fluctuations up and down during it. Meat continued its deflationary trends. And produce, while deflationary for the quarter, showed inflation in the last 4 weeks of the quarter, and pharmacy was inflationary. As a result, we increased our expectations for LIFO to $80 million, a $55 million increase over our initial expectations.
We have also made some incremental investments in price in certain markets that had very hot features on milk and eggs. While this affects gross margin in the short term, it is less expensive than regaining a customer's loyalty later on. These 2, plus the incremental investments in hours and wages, are the primary factors causing us to lower our guidance for the year. Our GAAP net earnings per diluted share guidance for 53 weeks is now $1.74 to $1.79. Our adjusted net earnings guidance range is $2 to $2.05. The previous adjusted net earnings guidance range was $2.21 to $2.25. See the Form 8-K we filed this morning for additional information on guidance.
Because this is an unusual year, we're going to provide a quarterly cadence relative to last year rather than compare it to our long-term guidance rate as we've done in the past. For net earnings per diluted share, we expect the second quarter to be down compared to last year, the third quarter to be up slightly compared to last year and the fourth quarter to be flat excluding the 53rd week. We continue to expect identical supermarket sales, excluding fuel, to be flat to 1% growth for 2017, and we continue to expect capital investments excluding mergers, acquisitions and purchases of leased facilities, to be in the $3.2 billion to $3.5 billion range for 2017. Over the long term, we remain committed to achieving a net earnings per diluted share growth rate of 8% to 11% plus a growing dividend.
Now I'll turn it back to Rodney.