After attending a debate yesterday at UOttawa (Fork vs. Feet) I recalled an important principle of physics (thus, of science in general) called the first law of thermodynamics. Very simply put, energy in = energy out. I have, for some time, believed that this is a critical concept that must be understood by any individual interested in weight management- I, along with the large number of health professionals, still believe this today.
The first law of thermodynamics is, to simplify, an expression of the principle of conservation of energy, which states that the total amount of energy in any system remains constant over time: thus energy cannot be created or destroyed. For weight management, this is very important to understand- stored energy as fat simply will not be destroyed (or broken down) without conversion to a more useful form, such as work (exercise) or heat. The latter won't likely make you lose weight- dehydration may kick in first.
Fat is probably the most efficient form of energy storage in the natural world (to the misguided fool who argues that it is glycogen I have 3 words: water of hydration). We humans are truly storage machines- an evolutionary trait that allowed us to maintain energy stores during times of famine when eating infrequent meals- we wouldn't be here without it. But back to the point- stored energy as fat cannot be "burned" without actually burning it!
There are two sides to the coin though...the energy in side of the equation also plays a role and is just as important to understand for one interested in weight management. I would recommend simply thinking about the food that you are eating and ask yourself questions such as: how much of this is natural, or free from processing? How many of the ingredients are 'artificial'? Can you identify, within reason, the exact source of the food, ie/ wheat, oats, beef, etc (if not, it is probably too processed). Questions such as these, as well as others, should form the basis of thought concerning one's food intake- forget dieting, forget cutting food groups, such as carbs...just think a little bit more about the energy in side of the equation.
When in doubt, consider a primitive, ancestral 'you' and their dietary habits- would early humans eat Mars bars, ice cream, or pre-packaged 7-cheese lasagna (yes, even if it's PC blue menu)...I didn't think so. They would likely eat whole foods with natural ingredients and plenty of nutrients...a poor argument to make for choosing foods at the grocery store, but I think it is important to keep in mind what humans are meant to eat. After all...it's us who is eating it.
In sum, an anthropocentric society would have people believe they are above many of the laws of the universe...the law of thermodynamics is not one them. Energy in continues to equal energy out...