There are two types of fat in your body: Brown fat and white fat. The brown fat is a type of fat that BURNS energy. The white fat is a type of fat that STORES energy.
If you were to choose one, which one would you want more of? Yeah, the brown one, right? If only it were that easy! Brown fat is not common in modern adult humans. But, perhaps, they just aren't common in the typical American eating the typical American diet, full of sugar and starches. Let's face it, we have an obesity epidemic on our hands.
How can we turn our white fat brown? There aren't many options that we know of. But, as some of you biohackers may know, exposure to cold will stimulate the production of brown fat cells in our bodies. We call this "shivering thermogenesis". Maybe I should pick up cold showers again...seems like a good way to get more brown fat! Scientists are working hard to find a weight loss drug that can help "brown" our white fat cells, but more natural strategies may be the key.
Intermittent fasting is one such natural intervention. Intermittent fasting raises ketones, decreases inflammation, triggers autophagy and production of new brain cells. Guess what else it does?
It can turn your white marshmallow fat tissue nice toasty and golden brown! Take a microscope and look at the color of the white fat cells before and after fasting...the latter is more of a brown-ish color.
We talked about alternate day fasting in humans in a previous HVMN Journal. Eat all you want one day, fast the next day, rinse and repeat. In this landmark Cell Metabolism paper, we are going to look again at every other day fasting (EODF) in mice. The intervention group (the one that gets to feed and fast) (EODF) did 15 cycles of this, for a total of 30 days. Of course, the control group gets to eat "ad libitum", or "all you frickin' want, when you want", which I will abbreviate as AYFWWYW.
What did we find? Both groups ate the same amount of food, and the EODF group weighed LESS than the AYFWWYW. Ok, you "calories in calories out" enthusiasts, how do you make sense of this?
Where did the energy go?
Indeed, the EODF mice had a higher total energy expenditure compared to the AYFWWYW group! The EODF expended much less energy on fasted days, but expended much more energy on the feeding days, but OVERALL, the EODF expended more energy. How?
[Aside: Your "total daily energy expenditure" or TDEE can be split up into four major parts: basal metabolic rate, exercise-associated thermogenesis, non-exercise activity thermogenesis, and diet-induced thermogenesis. Basal metabolic rate is the minimal amount of energy you need to function. This is largely determined by your muscle mass. Thermogenesis means "making heat". You can make heat by moving. Moving is basically divided into planned movements (like exercise) versus unplanned movements (for example, walking, talking, picking your nose, or just being fidgety). You can also make heat by eating. Yeah, that takes work too! Perhaps, an argument for nutrient dense foods here, but I digress...]
Let's go back to those mice. What was the body composition? The EODF mice maintained lean muscle mass. That means basal metabolic rate is similar between the two groups. No loss, no foul, right?
That means, the EODF group had more "thermogenesis". And indeed, they did generate more heat. How do we know? It's not pretty, but sticking a thermometer into the rectum of those mice gives us continuous tracking of their circadian core body temperatures. The rectal temperatures of the EODF group were higher than the AYFWWYW group.
Which type of heat was expended? Did the EODF group exercise more compared to the AYFWWYW group? No. Did the EODF eat more than the AYFWWYW group? Well, we already established that they ate the same amount, but they ate in DIFFERENT INTERVALS.
The clue lies in... FAT BURNING! How do we know this? We can measure the fat in these mice... and we can perform indirect calorimetry.
[Aside: What is indirect calorimetry? Well, strap on a mask in a closed system, and we can measure how much oxygen you breathe in, and how much carbon dioxide you breathe out. Scientists use this non-invasive method to measure the ratios of gas exchanged, which can be used to calculate your energy expenditure and metabolism, whether you are sleeping or riding a bike. Guess what, it's not always one to one, and it differs based on what type of fuel you are burning, and what type of food that you are eating. If your ratio is close to 1, you are a sugar burning machine. If your ratio is closer to 0.6 or 0.7, you are a fat burning machine. Usually if you are eating a mix of both you fall in the middle.]
Let's go back to the mice. Indeed, indirect calorimetry was performed on the the mice. What were the results? On average, the exchange ratios were lower in the EODF group compared to the AYFWWYW group, which means they were burning MORE FAT! The major fuel they were burning was more fat...and less sugar.
Back to the microscope. If you take a look at their adipose, or fat, the EODF group lost more fat around their groin, but way more around their heart and their stomach regions, than the AYFWWYW. The EODF group had MORE brown fat and turned the white subcutaneous groin fat BROWN. Also, these transformed fat cells had two prominent features of brown fat cells: More lobules to them (Think fat cells with baby fat cells attached to them.), and higher amounts of an uncoupling protein called UCP-1. This protein uncouples the protons moving down the mitochondrial gradient from the synthesis of ATP, allowing the energy to be dissipated as heat. Isn't this considered inefficient? When all the energy is being transferred to heat? Y can either you store it, or your burn it as heat. This process is called "nonshivering thermogenesis", since you are making heat without muscle shivering.
So, this study suggests that if I do alternate day fasting (I eat all I want on one day, and then fast all day the next, etc.)
Wait, this seems too good to be true…
Well, no. This study was done in our mice counterparts, so how much of it can apply to humans? We have to take this into consideration when we are quoting studies, but this is pretty interesting nonetheless!
Authored by Dr. Manuel Lam
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