Carb Cycling Followup
Thursday, October 25, 2012
I left things kind of vague in my last blog because I wanted to try this out for a couple of weeks before getting too detailed. It resulted in some very good questions, though. So I'll explain the concept of what I'm attempting.
Those of us who do low-carb primarily focus on lowering insulin levels in order to induce fat loss. However, there is another hormone that is instrumental in adipose fat tissue levels: leptin.
We are very complex biologic systems, so there are tons of biochemical interactions. The gist of it is insulin and leptin are hormones that directly effect the amount of adipose fat tissue we carry.
Elevated insulin levels turns on fat storage. Too much insulin circulating chronically can lead to insulin resistance.
Leptin is one of the hormones involved with hunger and satiety. It is also responsible for up and down regulating metabolic burn. The amount of leptin circulating is proportional to the amount of fat we have. Leptin lets the brain know that we have sufficient fat stores, so no need to eat anymore. Low leptin makes us more hungry, and slows down calorie burn.
However, just like insulin, when levels are elevated for prolonged periods of time, we can become leptin resistant. Our satiety switch doesn't work. We become chronically obese, and we can't burn fat. We have too much fat, and yet our brain keeps telling us to eat more and more.
I remember when I used to battle with 'willpower' to stop eating. It was always a losing fight. It's chemical. Obesity is a miscommunication of hormones that chronically increases fat and prevents fat burn.
Here are some ways leptin is lowered:
- Very low calorie diets
- Very low carb diets
- Insufficient sleep
- Strenuous exercise
Ever felt crazy hungry after a hard workout? Yep, that's lowered leptin levels compelling you to eat.
So how do you raise leptin?
Well, the bad news is leptin levels drop at a much faster rate than it increases. Once leptin levels crash, it is very hard to raise.
I've only recently started exploring the leptin theory, so I don't know all the ins and outs. The only thing I've seen on how to raise leptin is to not be hungry. When we feel 'full', enough leptin is triggered for our brains to say 'stop'.
- If you restrict calories, periodically have a high calorie day.
- If you low-carb, periodically have a high carb meal.
- Eat lots of fiber so you feel full, and leptin is stimulated.
- Have a rest day to clear out cortisol and other stressors (more about 'rest' days later!).
Once leptin levels plummet, it's an uphill, against the wind battle to restore it. So it's best not to get into that situation. This is but one reason why anorexics gain fat at an accelerated rate if they go back to eating 'normal' after prolonged severe calorie restriction.
Never EVER starve yourself to lose weight.
This might also be why chronic cardio goers tend to plateau despite vigorous exercise. Leptin lowers metabolic rate to counteract increased energy expended and decreased calorie consumption.
This is the idea behind carb cycling. Very low carb/calorie days clears out elevated insulin levels, but also drops leptin. High carb/calorie days raises leptin, but also raises insulin. Thus follow with very low carb. Wash, rinse, repeat as necessary.
Presumably this works better for people near goal weight because they are less likely to have issues with insulin resistance, which is a primary block to fat burn. For people just starting weight loss, an 'induction' period is a very good idea so there is a clean slate.
Some people may call this a 'cheat day'. I caution against that as an excuse to binge. I plan to use my high carb days to eat mainly starches: potatoes, sweet potatoes or rice.
As for why to sync up high carb with high intensity workouts, one reason might be because HIIT depletes glycogen stores. The more strenuous the workout, the more glycogen burned (and the more leptin dropped!). High carb/calorie, in theory, should replenish glycogen, and offset some leptin drop. Carbs/calories are used in a beneficial way, and hopefully less likely to be stored as fat.
This is what I'm attempting for the next few weeks. In my case, I'm hoping it will up-regulate metabolic burn.