1) HIIT is Better than Moderate Cardio
There's no evidence that high intensity cardio is better than moderate cardio. Purely anecdotal.
Yes, you can burn more calories in a shorter period of time when increasing intensity. But when intensity increases, volume and frequency must decrease. So since you must do less, it all averages out about the same.
Moderate cardio is easier on the joints, CNS, recovery, and is proven to be effective.
Yes many lean people do high intensity cardio, but to paraphrase Lyle McDonald "Many lean people do HIIT, but they're most likely lean because people willing to do HIIT consistently are most likely willing to follow a diet."
2) Low Carb Diets are the Best Diets
Low carb diets force people to eat more protein, and make it hard to overeat.
Whey you're left with only meat to eat, you'll be getting more than enough protein.
It's also hard to overeat and snack on rib eye steaks and grilled chicken.
Which is the only reason it works.
If you wan to do it go for it, but it's miserable and unnecessary.
It's just a food restriction.
3) Gluten Causes Fat
Again, just like the keto/low carb/paleo/Atkins/ect. diet, all the foods that have gluten are the foods people overeat.
Get rid of those foods and it's hard to overeat. Yep, the same as the low carb diet.
Only people the few people on earth that are allergic to gluten need to avoid it.
Just another new thing to demonize and market some stupid book. And the're plenty of idiots that capitalized selling this to other idiots.
4) High Reps Mean Lean Muscle
There's no such thing as lean muscle. Terms like toned, and lean muscle are nothing but marketing terms that don't actually mean anything.
Purely used to sell fitness to women because they're often scared to get too bulky, which again, is not something real.
Women like this, who swear they're drug free natural lifters are what scare women. They're on plenty of steroids, but since they say they're not women are scared they'll end up looking like this from lifting weights.
Muscle is muscle, unless you are on steroids you don't have anything to worry about. Keep your body fat low, lift weights, and you'll be lean with muscle.
5) Ab Workouts for Six Pack
Abs are small muscles, working them only helps with core strength.
Core strength is great, but won't help you with a six pack or obliques.
Losing body fat is the only thing to reveal your hidden abs and shed your love handles.
They'll be plenty of scammers marketing abs books, ab workout bootcamps, etc. for those stupid enough to believe it. If you like overtraining a small muscle and wasting money and time, don't let me stop you.
The Fitness Industry is 98.6% Bullshit. So beware at all times.