Calories, HIIT and Mythbusting
What burns calories? Few commercialized areas of science are so filled with myths as that focused on weight loss. Everyone wants a easy, harmless, no-willpower answer. Someday, we may actually get one. For now there are no magical cures. But there are a fair few myths that need to be destroyed.
You may have read this one: eating ice cream actually results in fat loss. The hypothesis is that since ice cream is freezing, and it takes energy to heat it up, your body is using this energy while eating the ice cream.
Your body does certainly need energy to heat up ice cream, and even to properly digest it. Anything the body does requires energy, that's fundamental physics applied to physiology. But the devil is in the details. Consuming ice cream, usually high in fat and sugar, takes in a substantially greater amount of energy than are used to heat and digest it. Sorry, you still need to go easy on the dessert.
Occasionally ice water replaces ice cream in the myth. True it has no sugar or fat, so you're much better off and drinking a bit of extra water while exercising is always a good thing. But the energy required to warm it to body temperature is negligible in terms of the weight loss effect. Its just not going to spike your metabolism enough to lose weight. However, sometimes you feel hungry when in fact the body is just slightly dehydrated. Drinking water can cause you to feel less hungry, and it's much lower in better for you than regular soft drinks or even fruit juice.
Or, you might have heard this one: adding a pound of muscle makes the body burn an extra 50 calories. Not only not true, but meaningless. 'Burns 50 calories' over how long? And doing what? Just sitting watching TV consumes about 70 calories per hour. The body is always consuming energy to maintain internal temperature, restore cells, pump blood, etc.
A pound of new muscle will burn at most a dozen calories per hour. Still, putting some extra muscle on is a good idea, to do so requires high effort - either through weight training or HIIT. The standard male will use about 350 calories in an hour long work out; you can get through more than 350 calories in a 20 minute HIIT workout. HIIT also raises the metabolic rate for a day, burning about 250 calories more than if one hadn't exercised.
The reality is that if you take in more energy than your body uses the remaining energy is stored, generally in the form of fatty tissues. When the body requires more energy that you've supplied, it will turn to those fat stores in order to get some needed energy. That leads to lower fat in the body and weight loss. HIIT focuses on this process and tunes the body into maximizing this process.