Fast Food Without Seed Oils: Which Chains Actually Cook Differently

"Seed oil" isn't a precise scientific term, it's shorthand people use for a handful of industrially refined oils like soybean, canola, corn, and cottonseed oil that show up throughout fast food frying and food prep. A small number of chains have made public commitments to cook with something else. Here's what they've actually said, with sources, and where the picture is more complicated than the marketing suggests.

Steak 'n Shake switched to 100% beef tallow for its fries in early 2025. Five Guys has used 100% peanut oil for decades. In-N-Out fries in 100% sunflower oil, which is botanically a seed oil but has a different fatty acid profile than soybean or canola. Chick-fil-A fries its chicken in peanut oil but its waffle fries in canola oil. Sweetgreen moved to olive and avocado oil for cooked proteins and vegetables starting in 2023.

Which fast food chains have publicly moved away from seed oils?

Is sunflower oil actually a seed oil?

Yes, botanically. Sunflower oil is pressed from sunflower seeds, so it belongs to the same broad category as canola, soybean, and corn oil. The distinction people who avoid seed oils tend to draw is about fatty acid composition and processing intensity rather than plant origin. Sunflower oil is higher in monounsaturated and polyunsaturated fat and requires less chemical processing than soybean or corn oil, which is why some seed-oil-avoidant diners still consider it a better option, even though it doesn't meet a strict "no seed oil" bar. Peanut oil, by contrast, comes from a legume, not a seed crop, which is why it's generally excluded from seed oil criticism altogether.

What does the actual science say about seed oils and health?

This is genuinely contested, and it's worth being straight about that rather than picking a side. The core claim from seed oil critics is that linoleic acid, an omega-6 fat abundant in soybean and corn oil, promotes inflammation in the body. Mainstream nutrition researchers largely dispute this. A 2025 study of blood biomarkers in nearly 1,900 people found that higher linoleic acid levels were associated with lower inflammation and better cardiometabolic markers, not worse. Researchers at Johns Hopkins Bloomberg School of Public Health have summarized the evidence similarly: diets higher in linoleic acid are generally linked to lower, not higher, cardiovascular risk.

Where critics and mainstream researchers actually agree is on the bigger picture: seed oils are cheap and used heavily in ultra-processed food, and ultra-processed food as a category, high in refined carbohydrates, sodium, and added sugar, is consistently linked to worse health outcomes. Whether the oil itself is the mechanism, or just a marker for a broader category of food, is where the real disagreement sits.

Why are chains making this switch if the science is contested?

Consumer demand, not a settled scientific consensus, appears to be the main driver. Steak 'n Shake's own announcement framed the tallow switch around taste and "authenticity," tying it to how fries were cooked before most chains switched to vegetable oil for cost reasons around 1990. Sweetgreen's January 2025 menu launch leaned on language about "real food" and ingredients customers "feel good about." Whatever the underlying science, chains are responding to a real and growing customer preference.

How can you verify what a chain actually uses?

• Check the chain's own allergen and ingredient pages, most major chains publish these, rather than relying on secondhand claims.
• Look for a specific named oil ("100% peanut oil," "beef tallow") rather than vague marketing language like "clean" or "wholesome."
• Remember oil use can vary by menu item within the same chain, as with Chick-fil-A's chicken versus its fries, so check the specific item you're ordering.
• Be aware that oil sourcing can change. Chains update suppliers and formulations, so a claim that was true a year ago is worth reconfirming.

Frequently Asked Questions

Does In-N-Out use seed oils?

In-N-Out fries in 100% sunflower oil, which is botanically a seed oil, though with a different fat profile than soybean or canola oil. It's not accurate to call In-N-Out "seed oil free" in the strict sense, even though many people avoiding industrial seed oils consider sunflower oil an acceptable middle ground.

Does Chick-fil-A cook everything in peanut oil?

No. Chick-fil-A's chicken is cooked in peanut oil, but its waffle fries are cooked in canola oil, which is one of the oils most commonly flagged by seed-oil-avoidant diners. Check the specific item, not just the chain's reputation.

Is beef tallow actually healthier than seed oil?

That depends on what you're optimizing for. Tallow is higher in saturated fat, which mainstream cardiology guidance still recommends limiting, while seed oils are higher in polyunsaturated fat, which most current research links to better cardiovascular markers. Neither is a clear-cut "healthier" choice by every measure, and both are used in dishes, fries, mainly, that aren't a health food in either case.

Sources

• Steak 'n Shake to Use 100% Beef Tallow, PR Newswire
• Why Five Guys Exclusively Uses Peanut Oil, The Takeout
• How Many Ingredients Go Into In-N-Out's Fries, Tasting Table
• What Oil Is Really in Chick-fil-A's Fryer, Food Republic
• Sweetgreen Pushes Protein and Seed-Free Oils, Restaurant Business
• The Evidence Behind Seed Oils' Health Effects, Johns Hopkins Bloomberg School of Public Health