OK not every, you can diss the rest below.

Paleo

The return to monke diet. This is one of the most popular. The entire rationale behind it is just wrong and silly although the diet itself is accidentally not absolute trash. The main idea is that you should eat more like paleolithic humans because our body never evolved to eat the stuff that became available with farming, such as dairy, legumes, grains, processed oils, etc. This can have some advantages over the diets of the average person who eats trash, mostly because it avoids some really garbage processed foods and sugars etc. However there are several things wrong with it. First of all the whole "its what the cavemen ate so it's better" is basically a refined form of naturalistic fallacy and it's not supported by any scientific data. But even if it was true that it's best to eat like our ancestors did, it would still wouldn't say much at all because there was incredible variation in what paleolithic humans used to eat, according to location. Additionally, modern research shows that they did eat grain and wild legumes etc earlier than previously thought. Also, obviously humans evolved to adapt to changing diets pretty fast, which is how so many of us have lactose tolerance. So the thesis is just wrong on every level. But nonsense rationale aside, how good is it? I for one have no idea why you would want to specifically exclude legumes from your diet. I can maybe understand the rest (although if you're not vegan and don't have lactose intolerance excluding dairy altogether is not very smart either) but why the fuck would you exclude fucking legumes? There is no good reason. Legumes are major components of diets which have demonstrated to have health benefits, like the Mediterranean diet. Legumes are a good way to get protein and other important stuff without having to eat meat all the time. Legumes don't destroy the environment either, at least compared to other stuff we eat. Legumes are good. Eat legumes. It's 2021 ffs. You're following a restrictive diet already, at least have your restrictions be reasonable instead of nonsense. So it's mostly a grift but at least not a terrible one.

Carnivore diet

Similar rationale to paleo, but more wrong plus more fragile masculinity, and actually very bad for you unlike paleo. Basically everyone who follows this because they read about it on the Internet or whatever ​and not out of necessity or tradition ​is not to be reasoned with and should be rounded up and either put into a zoo or released into the wild, far from human society.

​Carnivore diet sickos who eat rotten meat

Same with vanilla carnivore diet except its practicioners should be shot on sight before they bite someone and give them some fucked up disease that was thought to be extinct.

Keto/zero carb diets

Restricting carbs can be good for weight loss sometimes, again mostly because the average person in the west gets their carba from the shittiest sources possible. The "I must avoid all carbs at all costs" psychosis is weird and funny and just not very good, especially when it leads to people skipping on stuff that's actually important for them jsur because they have some carbs. The funniest thing is when gym bros obsess about carbs. Anyone who knows athletes knows that they eat truckloads of carbs. Gymbros avoiding carbs at all costs are hurting themselves and their muscle growth because carbs act to preserve tissue protein because your body uses them for energy isntead of the protein. If you don't eat enough carbs you strain your muscle protein levels as well as your kidneys, because they have to excrete the nasty byproducts of protein breakdown. There are diets which are low in carbs but not so criminally low that they have adverse effects like that, however they haven't been demonstrated to have particularly beneficial effects either. Still, it may be a good idea for weight loss, mostly because it is more straightforward to follow it practically for some time. Not so much for the long term. Again, mostly a grift.

Fasting diets

Another one of the "why the fuck are you doing this when you can just not do it" sort. Just eat ffs. A good diet is one you can comfortably follow for the rest of your life. No one but the bad kind of sickos can stick to eating every second or third day or whatever for the rest of their lives, and you'll probably completely mess up your body in the process of the diet anyways. Stop torturing yourself, jeez.

Breatharianism/sun diet/Inedia/prana

OK this one is by far the dumbest. Yes, even worse than the rotten meat one. Breatharianism is kinda like intermittent fasting etc, except you also fast the rest of the days too. Yeah. "But if I do that I'll just starve and die" you say. Correct. That's exactly the problem. And yes, people have done that and they died. Why? I don't know. They believe they can survive by "feeding" on sun's energy and the air like a fucking lettuce. Newsflash, people aren't lettuce. I don't know why this is lost on some people. Apparently a lot of grifters in places such as India and weird American hippies pretend to have been living like that for years, but obvious bullshit is obvious. I rember reading a dumbass times of India article which said some stuff along the lines of "well, a pure sunlight diet is bad for you and you will probably die, but it's good to combine a normal healthy diet with the sunlight diet and find a healthy mean, because sun is good for vitamin D etc". Yeah, that's not combining prana with a normal diet, it's just a normal fucking diet but also maybe get out every now and then.

Bottom line, here's my epic health tips for the day: eat something every now and then because otherwise you will starve and die, that something should be something other than rotten meat, touching a bread crumb won't kill your gains and don't be the bad kind of sicko.