The Carb Refeed
The science behind the carb refeed is pretty simple. Being as we're all familiar with the Primal Blueprint, I'll assume we all know about insulin. Insulin is the storage hormone. It shuttles energy into our cells, amino acids into our muscles, and, unfortunately, fat into fat cells. We know that obesity is the result of chronically elevated insulin, and diabetes is the result of prolonged insulin resistance. The Primal Blueprint works by regulating our insulin and allowing our bodies to achieve homeostasis, which for the majority of us is a quite lean body.
The lesser-known but just as important hormone that drives body composition is leptin. Leptin does two major things:
1.) Leptin inhibits appetite
2.) Leptin tells our fat cells to release fat
As insulin levels rise, so do leptin levels. While insulin is shuttling fat into fat cells, leptin works as a counterweight and releases stored fat from fat cells, all the while telling your brain you are getting fuller and fuller. The end result for a person with a normal, healthy metabolism is no major net increase or decrease in fat storage after a reasonable meal. The very obese are typically highly leptin resistant AND insulin resistant. This means that while the people are very overweight, they are actually starving on a cellular level. The insulin resistance causes your hormones to store all the nutrition as fat in fat cells instead of energy in muscle cells. Then, the leptin resistance never tells our brain that we're full, and it never tells any of the fat cells to release any fat. The end result is a very overweight individual that is always hungry and suffers from malnutrition.
How much leptin that is in your system is correlated with how much fat is stored on your body. Overweight people have high levels of leptin in their system at all times, they are just resistant to it. As you minimize insulin production through eating Primally and your metabolism starts to heal, weight loss occurs. Overweight people lose large amounts of fat very quickly. It's not unheard of on this forum to see very overweight people lose 30 pounds or more of body fat a single month after going Primal! This is because their leptin levels are high. All this leptin in their system causes the body fat to melt off. As they become leaner and leaner, average leptin levels drop further and further. In short, the less fat on your body, the longer it takes to lose a certain amount of fat. Losing 10 pounds when you're 100 pounds overweight is easy. Losing 10 pounds when you're 15 pounds overweight is very difficult. This is because lean people have low leptin levels, so it's a lot more difficult to get those fat cells to release fat.
This is where the carb refeed comes in.
The carb feed works by temporarily boosting leptin levels. As leptin is insulin's antagonist, as insulin levels rise, leptin levels rise in kind. When you eat a prolonged low-carb diet, insulin levels are kept low and stable. The goal here is to shoot insulin levels through the roof for a small period of time. This will send the leptin levels sky high as well. Then, when the refeed is over and insulin levels regulate and you fall back into eating high-fat/low-carb, the temporarily elevated leptin levels, paired with the highly thermogenic effect of the starchy carbs (fats are for the most part non-thermogenic), your metabolism will be briefly elevated and let go of a little stored fat that normally would not get released. The goal here is to regularly reintroduce starches back into your system to keep repeating this effect. Over time, this results in huge losses in fat that may not normally be achieved.
Now, that all sounds fine and dandy, but it's not that simple. The trick here is that you have to fine-tune your refeed. A tall, muscular, highly active man may require 400g of carbs in a day to get the weight loss going. I've seen professional body builders require 500-600g of carbs each day. If you're a smaller woman with a desk job, you may need only 100-150g of carbs. As a 24yo, 5'7", 139lb male with a desk job but a very active workout schedule, I find about 250g of carbs is good for me. It varies, so you need to figure it out for yourself. If you overeat too many carbs, you'll store them as fat tissue and the carb refeed will backfire. If you don't eat enough carbs, the effect will not be strong enough and the carb refeed will backfire. This may require patience and trial and error, but if you figure out what works for you, the results will be worth it. This is consequently why you need to have a healthy, normal metabolism to attempt this. This is for losing those last pesky 10-15 pounds, or that stubborn body fat that just won't come off that problem area.
Timing also plays a HUGE role in the carb refeed. The key to being successful is to make sure these carbs are either burnt off or stored as glycogen for energy, not as body fat. This means that ideally, you will get all your carbs at your pre-workout meal and your post-workout meal. This is why the carb refeed days should be on your heaviest training days! That means the heavy weight lifting days, boys and girls. You shouldn't be doing carb refeeds on your low-level cardio days. You should be pairing these carbs with squats, deadlifts, military presses, benchpresses, calf presses...all the big, heavy, compound muscle movements that burn up your glycogen stores the most. If you do not lift heavy weights that often, a heavy sprint/HIIT session will also be adequate. Let's say you're an average American that works an 8am-5pm job, you eat breakfast, lunch and dinner and you work out after work. Your carb refeed day may look like this:
7am - small breakfast consisting of low-fat, a little lean protein, veggies and some fruit (25% daily calories)
2 pm - lunch consisting of low-fat, moderate lean protein and 1/3 of your starchy carbs for the day (25% daily calories)
6pm - heavy lifting work-out or hard HIIT session
7:30pm - dinner consisting of low-fat, lots of lean protein and 2/3 of your starchy carbs (50% daily calories)
Obviously, you would want to get your pre-workout meal as close to your workout as possible, but not too close that it'll inhibit your intensity. It's tough working out on a full stomach and your intensity will suffer, so use your judgment. I would shoot to get those starches in 2-3 hours before the workout. Now, if you do this right, not only do you get the beneficial insulin and leptin boosts, but you'll burn up the carbs in the pre-workout meal and the carbs in the post-workout meal will fit nicely in your glycogen stores and not spill over into fat storage.
You'll also notice that every meal is LOW FAT. That's right, ladies and gentlemen. FAT is our ENEMY on a carb refeed, and eating even moderate amounts of fat could cause fat gain. We are focusing on carbs here. Try and keep your total fat for the day under 40g!!! If you are a petite woman, you may want to shoot even lower, such as 30g of fat. Remember, this includes any fish oil supplementation. If you pop 3 fish oil pills a day, you have to subtract that 3g from your allowance. Your culinary friends during a carb cycle will be water, vinegar, cooking wines and lemon/lime juice as that is what you'll be cooking your meat in. Of course, dry pans, dry grill grates and oven roasting are even better yet. Just put that butter and oil away!!!
Don't put your trust in anyone on this forum, including me. You are the key to your own success.