Losing weight is easy, right? It's just Math, no? Eat fewer calories than you burn, isn't that the gist of it? So... who needs all this exercise stuff, right? Tighten the belt, fill up on rice cakes and low-fat peanut butter, suck it up for a few weeks, and the pounds should come sliding off...

Right?

Unfortunately, no, it's not that easy. That same human biology that evolved to keep our ancestors alive during the off-seasons between mastodon hunts works against us when we try to lose weight by starving ourselves.

You may be focused upon fitting into last year's bikini, but your body is focused upon survival. When it gauges that you have been under-easting over the course of a few days, your metabolism switches into an “energy conservation” mode, slowing way down. This translates into you feeling tired and unbalanced.

The human body is the consummate machine, and as such has numerous fail-safes built into its design. When it sees that its main tank of fuel – carbohydrates – is running on empty, it looks elsewhere for something to burn. And although a normal healthy person has a good 1 to 3 months of muscle tissue and fat that his body's engine may consume, he only has 1 to 2 days of glycogen stored up. Our red blood cells accept no substitute for glycogen. 

While glucose is the only fuel blood cells can run on, the brain will begin to adapt to power itself with ketone bodies made from fat. But to even meet basic energy needs, your body ramps up the breakdown of muscles and organs in addition to fat. This can be a big problem in the long run, because your body doesn’t distinguish between essential tissues (e.g., heart, kidney, blood cells) and less essential tissues (e.g.,  skeletal muscle). So, over time, this breakdown weakens and damages your vital organs.

Another problem with long-term fasting comes down to basic nutrition. It's really, really tough to get a full recommended daily allowance of minerals and nutrients when your diet consists solely of rice cakes and peanut butter.  Studies with anorexic patients have given us insight into specific deficiencies, which include calcium, iron, zinc, vitamin D and the B vitamins, in addition to dangerous electrolyte imbalances and protein malnutrition.

What's more, recovery is not as easy as you think. Once your body has down-shifted your metabolism, it will take a while to normalize, and you will be plagued by all the fatigue and irritability even while you are eating regularly.

So, eat smart, claim your 1,500 calories daily, get your proper nutrition, but exercise! Don't deny yourself that healthy big breakfast, just let the treadmill work it off of you.