The fact that at least 3 people in this thread have named the category "meal replacements" but not a single one has named a specific product I would know by name (non dieting!) seems to me a pretty clear indictment that this category is not as established as you are suggesting.

While I'd generally agree with you, you can look up any "meal replacement" shakes made for athletes that are used to add calories. They contain a large amount of protein and calories and are fairly well established. MET-Rx Meal Replacement is one of the larger SKUs on the market, but there are many others.

If it has a large amount of protein, it's not an actual meal replacement -- it's a supplement.

An average meal comprised meat and rice contains a large amount of protein. It's a relacement for that. What are you talking about?

Only about 25% of your daily calorie intake should be from protein. 60g a day for a 160lb sedentary person. Those high-protein shakes are usually around 60% protein. It is possible to consume too much protein.

So I say that it's a supplement rather than a replacement because it's not replacing a balanced meal. It's supplementing protein. A single protein shake can give a sedentary person almost 100% of their protein. That's great for active, athletic people who have higher protein requirements. Not great for sedentary people who have lower protein requirements.

Yeah, just like ketogenic dieting and no-carb diets are supplements.

What?

If you're a sedentary person, and you were to drink 3 of those protein shakes per day you'd end up with 2x your recommended protein intake and only but only 1/2 your recommended calorie intake. That's not a balanced replacement. It's a protein supplement.

Even on keto or no-carb, you still only get 30% of your calories from protein (same ratio as a non-keto diet, BTW). If you were to drink protein shakes all day you'd get 70% of calories from protein. The keto diet does not change the ratio of protein you consume. It only replaces carbs with animal and vegetable fats.

Too much protein is not good for you. It can damage your kidneys. It also causes weight gain, digestive issues, bad breath, and other things.

So again, I say that those shakes are a supplement, not a meal replacement, because they're not balanced. They're great for athletic and active people, because the more active you are the higher your protein requirement is. But a typically sedentary person should not use high-protein shakes as a meal replacement.

A ketogenic or no-carb diet only works if you completely abstain from carbs. If you have one or two keto meals a day, but not every meal, you're not doing a keto diet. Just eating a ton of protein.