Answering the question of “Is this keto?” is more complicated than one might think. While we use this as shorthand all the time, the real answer is that it is you who is or is not ketotic, not the food. If you eat the food in question and are still producing ketones after the meal has been digested, then you can say that the food “was keto” . . . for you, in that particular instance!
If you are overweight, restricting carbohydrates to less than 50 grams per day, and steadily losing weight, it is pretty much guaranteed that you are in ketosis. This is because your body fat is providing the necessary energy for your metabolic functions. As you get leaner or your protein and fat ratios become looser, things become more tricky.
Take bacon, the quintessential food that people associate with the keto diet. A typical least-restrictive keto ratio is two grams of fat for every gram of protein (2:1), but bacon is actually closer to a 1:1 ratio. This means that if you eat a pound of bacon, the high amount of protein might make your ketones drop if you’re not able to access the remaining fat grams from your body fat stores. There is only a certain percentage of stored fat that can be tapped for energy each day, and as you lose weight this number actually goes down.
If the total macros for that meal are a 2:1 ratio or better, then that meal is keto because it will produce ketones in your body. A significantly overweight person can eat more protein and still produce ketones, because they can tap their body fat more effectively as long as they are not raising their blood glucose with too many carbohydrates (blood glucose shuts off ketone production until the glucose is used up).
If you are a fat-adapted keto athlete, you can even eat candy before your workout and be producing ketones again shortly after the workout ends. So does that make sugary candies “keto”? Although it feels like sacrilege to even type, the truth is that any food can technically be part of a keto diet in small amounts. One bite of cake would not throw anyone out of ketosis for more than a few hours, but the problem is with the sugar cravings and impulse control problems that typically follow that first bite. If you have the willpower to frequently eat just one bite of high-carb foods, then you likely don’t need to be on any kind of weight-loss diet in the first place!
If you’re lean, then your total meal macros likely need to be at a 2:1 ratio or higher for you to produce ketones. Whether a food is keto or not depends largely on what it is in ratio with around it, and total calories matter too- excessive calories, even of pure fat, will eventually suppress ketone production. Ketosis is, after all, a metabolic pathway conserved to help us survive starvation.
So, to paraphrase Hamlet (a fitting name for these purposes): There is nothing either keto or non-keto, but the ratio makes it so.