Movie theaters are not making money on movies, they are making money on food.

On Tuesday, AMC Entertainment reported fourth quarter adjusted earnings and revenue that beat Wall Street estimates.

But admissions revenue, or money paid for movie tickets, actually declined 4.5% over the prior year as both ticket prices and attendance fell. And in a statement, AMC CEO Gerry Lopez admitted that the movies released during the quarter weren't all that great, calling it a "lackluster film slate."

So where did the company make money? Food.

During the fourth quarter, AMC reported concessions revenue rose 8.8% over the prior year to $215.3 million as average spending per customer rose 13.5% to $4.46.

In a note to clients following the report, analysts at Stifel put the strength in concessions into context like this:

Concessions were very strong: Even excluding the impact of a $5mn tax refund (aiding sales which are inclusive of tax), concessions were +10.9% with no margin erosion. The increase per patron (+$0.40/excluding tax) came from both new initiatives (+$0.25), ranging from the dine-in-theaters to bars to self-serve options while (+$0.16) came from a move to price excluding tax, similar to standard retail, allowing for price increases. For some sense of magnitude, the addition of a bar increases concession/patron at a venue by $0.35 alone. The result is that we anticipate a $0.40/patron concession increase for the first three quarters of 2015 based on these trends. With no increase to attendance estimates, this concession increase adds $50mn in EBITDA to our estimates.

Now, the question is whether this increased spending is being aided — getting what economists call a "tailwind" — from the decline in gas prices, as spending at movie heathers is right in the wheelhouse of the kinds of discretionary consumer spending economists expect to increase when the price of gas tumbles like it has over the last several months.

On AMC's conference call, Citi analyst Jason Bazinet asked if the company has seen increased spending due to the decline in gas prices, and AMC CEO Gerry Lopez responded saying, "I have honestly not thought about it in the context of what’s been happening at the gas pump."

In talking about the strength of the current quarter, Lopez said that right now, it's about the big movies that are currently in theaters: American Sniper, The SpongeBob Movie: Sponge Out of Water, and of course, Fifty Shades of Grey.

Lopez also noted that the strength of these movies helps the theaters because there is limited overlap in the target audiences.