This is a long one so grab some coffee and settle in!
Chapter / Rule 1 - Take Control with Proper Portions - 40/40/20
For Rule #1, Harper shows you the breakdown of macronutrients he wants you to be eating. 40% of you calories from carbohydrates, 40% from protein and 20% from fat.

Taken from teamripped.com
This is a fairly standard diet plan. 40/40/20 has been used as a starting point for many conscious eaters for ages. Go around on any forum or website and you'll probably see this recommendation. So when Harper states that he's
"...tinkered with this formula to get it right: I've tried different percentages, added, subtracted, split things up one week and then tried something new the next...I know this is the formula that will work."
he's basically full of it. He didn't come up with this "formula." But it sure does make him sound smart and science-y! On the other hand, I don't doubt that he's guinea-pigged many different kinds of diets and found this one to be the one that worked. Most of the dedicated fitness enthusiasts I know have tried all different kinds of diets just for the fun of it or out of curiosity. Self-experimentation is great fun if you do it right and it can teach you a lot about yourself.
However, I don't think that 40/40/20 works perfect for everyone. There are many happy people out there who do something like 60/20/20 or 20/60/20.
40/40/20 isn't a bad place to start though if you're not sure what you're doing, so I am pretty cool with his recommendation here. Many crash-diet plans you'll see involve much much lower carbohydrates than that!
Here's another thing I appreciate about this chapter: Harper has a couple of quotes about how no food is inherently bad -
"It's not that complex carbohydrates are evil or that you can never have them again..."
"Fats are not "bad"..."
So, thanks for that! In an age where sugar is the devil (although...he did say that fructose and sucrose are "twin demon-spawn" in his last book...hmm...) and saturated fats are going to clog your arteries, it's nice to hear a public figure say that there isn't anything bad or evil about two major macronutrients. Poor carbs and fats. All they ever wanted to do was be delicious.
He also mentions that protein is key for preserving muscle mass while losing fat. Very true as well.
Now onto the stuff he didn't get quite right:
"...protein helps control blood sugar and insulin..."
Protein stimulates insulin as much as, and in some cases more than, many carbohydrates. This isn't really common knowledge, but it certainly should be. So next time someone tells you that sugar and other carbs are bad because of insulin, point that fact out to them.
"...think of it this way: simple carbohydrates are found in fruits and vegetables...and are generally "good." Complex carbohydrates are what we find in processed starchy food - breads, baked goods, pastas, crackers and potatoes."
You may be asking yourself, "Wait, I always heard we wanted complex carbohydrates?" And you'd be right - in general that's been the advice doled out. Harper is kind of tripping over himself a little here. In his last book, he actually wanted you to eat whole-grain carbohydrates (Rule #4 - however he has made clear that this particular book is for special circumstances). Here's a summary of why the advice is typically to eat complex carbs instead of refined carbs:
- Complex carbs take longer to digest (due to fiber content and the fact that longer, more "complex" chains of carbohydrates take longer for your body to unravel and use)
- The longer they take to digest, the more satiated you'll feel and the slower your blood sugar will go up.
- This will lead you to be less hungry, thus consume less calories and lose weight.
So the reason that people don't generally suggest things like twinkies, pop-tarts, white bread and other refined carbohydrates is because, aside from their lack of nutritional value, they get digested quickly and cause your blood sugar to go up and crash back down. Sometimes this can leave people hungry and/or tired. Not generally things you want to be during a caloric deficit.
Fruits and vegetables do tend to be on the simpler side of carbohydrates. This is why some people will tell you that apples and bananas are going to make you fat or some shit. (Because they have a lot of sugar in them) However most sane people will realize that the fiber and nutritional content of them off-sets and potential 'negatives'. Plus they're delicious.

A basket full of simple sugars!
Harper could have been much more clear by leaving simple and complex carbohydrates out of the equation. If he had simply said something like "fruits and vegetables have a lot of fiber and water content, leaving you much more full than a twinkie on your ridiculously low calorie diet. So we're going to eat those instead of twinkies, woohoo!" instead of trying to sound smart, it would have made much more sense.
"You'll have an amazing, for-the-ages wedding album, a jealousy-inducing reunion photo, a bathing-beauty shot that your spouse just can't stop looking at!"
YES, WE GET IT, WE'RE GOING TO LOOK SEXY. Also, maybe it's just me, but I kinda think it's more important to look back at your wedding album with fondness not because of how tiny your waist might be, but because it memorializes the day you committed yourself to someone you (hopefully) love. Haha nahh, it's more important to look smokin'.
Moral: 40/40/20 macronutrient breakdown is sensible to start with and pretty standard. Not bad advice for someone just starting out.
Chapter / Rule 2 - Cut back on calories. Then cut back again.
800 calories a day for women. 1200 for men.
So you're a 6'0 female waitress on her feet all day? 800 calories.
5'2, 230 pound female track and field athlete? 800 calories.
That makes sense, right? I mean, haha, what are the chances of you blacking out in the middle of a shift at around day 18 of only eating 800 calories a day? The price we pay for beauty.
I'm going to make this perfectly clear right here:
Unless you are under the surveillance of a medical team, you should never, under any circumstances, intentionally eat only 800 calories a day for an extended period of time (say, 21 days).
Harper says that these are special circumstances and that if the calories weren't this low you wouldn't meet your weight-loss goals. That is probably true. Because if you're trying to lose a significant amount of weight or drastically change your appearance in 3 weeks, you need to change your expectations.
As a fitness professional who isn't interested in creating drastic, insanely fast weight loss for maximum TV ratings or to sell a crap ton of books, I'm going to tell you that there is NO NEED to ever drop weight that quickly unless you are under the guidance of a medical team. Your health and sanity is way more important than the need to look 2 inches slimmer in your reunion pictures.
Are you serious about losing weight? Then do it in a sustainable way that HONORS your health - mind and body. It will take longer, yes. But I PROMISE you will be better off in the long run. Honor your body by giving it the time it needs to change.
"[Diet experts and motivators] dress it up in pretty prose but never tell you the truth about the number of calories it takes (or doesn't take) to meet your goals."
Actually, most diet books and health magazines also give ridiculous calorie counts for women. 1,200 - 1,500 is pretty standard. For most people (especially those with a lot to lose), THIS IS STILL TOO LOW. Harper, you are just taking this one step further in the wrong direction.
He cites 3 different studies to back up his assertion that this is a safe, effective and sustainable way to lose weight. (By sustainable, he means that you can sustain the weightloss from this 3-week diet by going back over to The Skinny Rules diet after this program is done - basically he asserts that you will not gain back any weight from this.) Let's take a look at these studies:
Study #1
"VLCDs [Very Low Calorie Diets] produce greater improvements in glycemic control than more moderate diets, even if weight losses are the same. Better glycemic control means better weight control."
It is clear that Harper never expected anyone to look up the studies he cites. Because if you did look this one up, you'd find a conclusion that is the complete opposite of Harper's arguments:
"However, to date, it has not been possible to develop treatment programs that maintain this weight loss long term. Neither intensive maintenance sessions nor intermittent VLCDs have been successful in maintaining the benefits of VLCDs long term. Thus, from the perspective of producing long-term weight loss, balanced low-calorie diets appear to be as effective as VLCDs."
However, it is true that VLCDs produce superior glycemic control in obese diabetic patients. This is important for a diabetic since excess blood sugar is a dangerous problem for them. Diets like this are supervised by a full medical staff. If you do not meet both of these conditions, VLCDs are not for you. See the above quote that says VLCDs have not been successful in maintaining weight-loss.
Study #2
Thankfully for this second study Harper cites, we can get the full text. In this study, participants were put on a 800-calorie per day diet for 8 weeks. After this intervention, there was a 6-month maintenance phase. He read this study and concluded:
"positive metabolic changes that the low-calorie diet induced made weight regain much less likely."
The funny thing is, this study is only looking at participants who regained weight. So using this study as an example of how VLCDs don't cause weight regain is a bit odd.
I think this may once again be a case of Harper citing a study just to have something to cite and sound official.
The primary finding of this study was that participants who lost the most weight and those who made the best improvements in insulin sensitivity regained less weight. While this is certainly interesting and perhaps merits further investigation, it is a far cry from saying a VLCD will not lead to weight regain - especially considering everyone regained weight. Some just did to a lesser degree.
Study #3
This study is an examination of existing literature on VLCDs. It looked at 9 different trials to gather data. They concluded:
VLCDs ... with an average intake between 400 and 800 [calories] do not differ in body weight loss. Nine randomized control trials, including VLCD treatment with long-term weight maintenance, show a large variation in the initial weight loss regain percentage, which ranged from -7% to 122% at the 1-year follow-up to 26% to 121% at the 5-year follow-up. There is evidence that a greater initial weight loss using VLCDs with an active follow-up weight-maintenance program, including behavior therapy, nutritional education and exercise, improves weight maintenance.
In other words, within 1 year, some people lost more weight, some people gained more weight than they lost. After 5 years, no one had completely maintained their weight loss, with some again gaining more than they lost. They conclude that, when it comes to using VLCDs to lose weight, it is best to lose a whole bunch of weight then continue treatment with exercise, therapy and seeing a nutritionist.
Sadly a lot of us don't have access to those last 2 options. They certainly would be helpful in maintaining weight loss.
In any case, this study (I think, I could be wrong) was only looking at VLCDs, without comparing them to more modest diets. This is not sufficient to say that using a VLCD is the best plan. However, to assure you that this 800 calorie per day diet is a good plan, Harper concludes:
Short-term very low-calorie dieting can produce a whole bunch of positive changes that will keep you from getting fat again.
They can also be very difficult to follow outside of a laboratory and can produce a whole bunch of negative changes that will keep you from maintaining your hard-fought weight loss.
Moral: PLEASE DON'T ONLY EAT 800 CALORIES A DAY.
Chapter / Rule 3 - Eat no complex carbs after breakfast
If there's one thing I want you to get out of listening to me ramble about these books and nutrition in general it's this:
It's not as complicated as you'd think.
It doesn't matter when you eat. It doesn't matter too much WHAT you eat. What does matter is HOW MUCH you eat.
So rules like this annoy me. They end up confusing people, there's conflicting opinions everywhere, and for the person just looking to get a bit leaner they really don't matter. Sure you can argue about pre and post-workout nutrition a little, but if it confuses you or causes you stress you don't have to worry about it too much. Honest. Just do what you want.

I found this picture from an article talking about the evils of gluten. God stock photos are getting ridiculous. First it was "women laughing alone eating salad", now it will be "women looking terrified and guilty eating any kind of food."
"...sugar cues the pancreas to make more insulin. And that process triggers appetite!"
He's being a little contradictory - simple sugars, like the kinds you find in fruit and vegetables, tend to be the ones that would cue the insulin response. Yes, they have fiber and loads of nutrients and good stuff, but they are, in the end, sugars. Also as we went over before, protein stimulates insulin as much as and sometimes more than carbohydrates. So this point is kind of moot.
If he just said "we're cutting out grains of all kinds because they aren't very satiating for the calorie load" this would all be making a lot more sense.
"The later in the day you eat complex carbs, the more likely it is that you will get food cravings late at night."
I'm pretty sure if you follow this diet you're going to be having food cravings late at night, early at night, in the afternoon, late morning and early morning. Ya know, because you're only eating EIGHT HUNDRED CALORIES!!
Moral: Meal and macronutrient timing is really not super important. If you're more advanced when it comes to nutrition feel free to tinker, but if you're new to the whole thing, don't worry about it too much.