Carb Cycling is a relatively new dieting concept that is supposed to achieve the holy grail of body composition, which is to burn fat and build muscle at the same time. Many people that haven’t done their research would tell you its impossible, but eating in a certain way and structuring a proper plan with meal planning will allow a person to achieve this. The concept is relatively simple.
On days you lift you eat a high carb diet (around 2 grams multiplied by your body weight or more), high protein (at least 1 gram multiplied by your body weight) and keep fat low to moderate (likely around 25% of your body weight or around 40-50 grams). Carbs release insulin, fill out muscle glycogen, enhance energy, drastically elevate metabolism, increase testosterone levels by dropping SHBG, lower cortisol, increase leptin and many other benefits. Muscle glycogen needs to be topped off and the body needs to be in a state of cellular hydration in order to build muscle and carbs achieve both very well. Attempting to do this on high fat, low carb diet is very difficult. The increase in hormones, specifically leptin drastically improves fat burning in the body and only carbs can upregulate this. If your leptin is low, which commonly occurs in chronic low carb diets, you fat burning can be diminished by 50% within 3-4 days. Basically this high carb day upregulates all the hormones needed to build muscle and properly burn fat. Loading up on high fat diet doesn’t bring these benefits. Also the body doesn’t have a long term storage depot for carbs and protein (De novo lipogensis is not efficient in humans). This means that overfeeding this day, with fat kept low, means that the chances of putting on bodyfat are very low, especially only for one day. Sample foods for this day are all lean meats- chicken, egg whites, seafood; starches – bread, potatoes, pasta, rice, oatmeal and even some low fat or fat-free junk food in moderation.
On days you don’t lift, you eat a low carb diet around 100 grams or lower, high protein (1 gram per pound of bodyweight), and a higher fat intake (60-80 grams). This day you will be in a calorie deficit in order to burn fat. Since you are in a deficit your fat intake can be much higher than the previous day. You still want to keep carbs low on this day. The main reason is by depleting your body of carbs on the rest day, you make yourself more sensitive to the overfeeding of the high carb day “by making room.” Also, since you overfed the previous day, eating a lower carb diet is very effective for burning fat. Another reason to increase fat intake on this day is for hormonal reasons, the benefits of fat and dietary variety. Fat has a lot of benefits and since your focusing more attention on carbs on the lift day, you need to make sure you eat them on the rest day for the benefits they bring. Also, eating fattier foods on your rest day, will appease your cravings and improve diet variety, so you don’t crave them on a high carb day. Sample foods for this day include fattier meats – red meat, whole eggs and veggies.
The beauty of this system though is that each day compliments the next. The high day offsets the negatives of chronic dieting and the low day allows dieting days to remain very effective as well as preventing fat gain from too many high days in a row. This system works very well on an every other day setup. For example, lifting days would be Monday, Wednesday and Friday and rest days would be Sunday, Tuesday, Thursday and Saturday. Eating in this fashion over the course a week allows for 4 fat burning days (which remain effective since the high carb days upregulate metabolism and hormones) and 3 days for building muscle (which remain effective as the low carb days make the overfeeding days more effective and prevent excess fat gain, while building muscle.)
This system can be easily manipulated to either build more muscle or burn more fat. For example, if one wanted to gain more muscle simply do 4 high days and 3 low; 5 high days and 2 low days or if more fat burning is desired then do 2 high days and 5 low days. Always keep at least two high days on a diet. The high days are too important to skip. 3 low days in a row followed by a high day would be a good cycle for someone focused on more fat loss.
As for calories a very effective setup would be to find your maintenance and eat +20% on high carb days and -20% on low carb days. Another very quick rule of thumb is to find your BMR and add 800-1000 calories over this on high carb day and eat at your BMR or -100-200 calories less than your BMR on low days. A quick example for someone who weights 160 lbs would eat about 1600 calories or a bit lower on low days and 2400-2500 on high carb days. I’ve seen some recommendations to go +30% on high days, but that seems a bit too much and unnecessary. If you only need 2500 calories to build muscle then eating 3000 calories isn’t doing you any favors and will probably just increase fat gains.
A quick note on Leangains.com – Martin Berkhan created a system very similar to carb cycling. Berkhan is at 5.5% bodyfat at around 200 lbs, but has “former fat boy”genes that many people have (including myself). Berkhan overcame his own dieting issues and has done a ton of personal research, but its pretty inspiring to see someone maintain this level even with subpar genes. Berkhan fasts for 16 hours a day and feeds for 8 hours a day. I’m not a big fan of fasting, so I don’t, but overall his system is a twin brother to carb cycling. The reason I bring up Leangains though is because I’ve read many of his free articles and his website is nutritional goldmine. The most important thing I learned from his site is that eating in this fashion attains all the benefits and none of the negatives of all diets. Two more important things I learned from Berkhan are a very low level of exercise is needed to obtain the body of a Greek statue and the awesome information on carb refeeds. It seems that one refeed a week is not enough to prevent all the negatives of dieting. Also one cheat meal isn’t a long enough period of time to reverse the negatives either. That’s why refeeding with high carbs at least 2-3 times a week for a period of at least 6-8 hours is needed to reverse these negatives. And refeeding on lifting days allows one to build muscle mass while losing fat. Pretty awesome combination that many used to think impossible.