Don’t get too excited. Remember that in order for it to be considered a cheat it has to be an abnormal part of your diet. But when part of a normal low carb, high protein diet a well timed cheat can actually be a useful tool. For this to work there are a few rules. The first rule is that cheats should be no more frequent than twice per week. Once per week is best for most people. This should be a single meal, and can be anything that you want: chocolate cake, brownies, french fries, whatever.
Without getting into the physiology behind how this works, essentially, a single load of sugar is bit like throwing a little gas on a fire. It makes it get very hot, and use fat up for energy at an accelerated rate for a 24-48 hour period of time. This is why most body builders look the best the day after their competition. They stay ultra strict for about 6 weeks before a competition. This forces their body to utilize their fat stores for energy, helping them lean down. That is great but the long stretch without carbs causes their muscle to loose glycogen stores, reducing energy for workouts and making them look flat (glycogen attracts water, which makes the muscle cell look full). In addition, they will go into ketosis forcing their bodies to use up that hard earned muscle as energy. Then they go into their competition looking tired and deflated compared to only weeks earlier. After the competition, they go to IHOP and eat like they’ve spent the last 5 years in a concentration camp. When asked how they did, “Ok, I scored where I thought I would, but the next day I looked great! Wish I had gone in looking the way I did the day after, would have done a lot better”. Even after dozens of competitions, they make the same mistake.
I actually saw this for the first time a s a teenager just getting my feet wet in the field. The guy that I had been working for at the local gym was a retired body builder and college strength coach. He hadn’t competed in quite a few years but still looked great so we talked him into giving it one more try for fun. He leaned done to a ridiculously low body fat percentage and dropped to around 195 (he was crazy lean before he even started cutting at 225), but looked a little flat for the competition. Fortunately, everyone else made the same mistake so he won. The next day he looked absolutely amazing. This was a guy with almost 20 years of experience competing. That was the first time that I saw it, but I have seen it countless times since, even in guys that everyone else go to for advice (and pay for it, in cash and bad advice).
The purposeful cheat will do 3 things, fill the muscle up, provide ample energy for the competition, and most importantly help them to loose that extra percent of body fat. This same tactic can be used weekly to continuously lean down, provide ample fuel to recover from hard workouts, and look extra good for the day at the beach on Saturday.