This question is a combination of physics, chemistry, biology, and fitness. Taken in three related parts, it can be expressed as 1) If I eat a pound of butter, I gain more than a pound of fat, so where does the extra mass come from? 2) People talk about fat "changing" to muscle, but muscle weighs more than fat, so where does that extra mass come from? and 3) When I lose weight, is the mass burned for fuel, and if not, what happens to it? I would prefer a brief explanation with links to some fitness or biology-oriented websites that explain these processes (I already have plenty of sites about chemical reactions and conservation of matter, this is specifically regarding biological processes, and the person I'm trying to explain this to is not satisfied with general chemistry and physics examples).
I assume that what you are looking for is a "plain English" explanation to answer your questions so you can explain them to your friend. I'll do my best! I'll address your questions in order --- 1) If I eat a pound of butter, I gain more than a pound of fat, so where does the extra mass come from? This is a common misconception among dieters, but not true. Plain and simple, you can't possibly gain more weight than the weight of the food you eat. If you eat a pound of food (ANY food, whether butter, carrots or a juicy hamburger), you will temporarily gain a pound, but no more. Then, as your body burns up calories, that initial weight gain decreases. The number of calories in the food versus the amount of energy you expend will determine how much of the original pound of food you retain. For example -- a pound of fat equals about 3500 calories. A pound of carbohydrates equals about 2000 calories. If you eat a pound of fat you will retain the full pound. If you eat a pound of bread or apples (mostly complex carbohydrates, the good stuff) you will only gain 4/7ths of a pound. In any case, you can never gain more than the original pound you have eaten. So, there is no "extra mass" gained. 2) People talk about fat "changing" to muscle, but muscle weighs more than fat, so where does that extra mass come from? Again, this is a myth. Fat does not turn into muscle. Muscle does not turn into fat. Biologically they are two different kinds of cells. The kind of cell you build, fat or muscle, depends on your exercise regime and the food you eat. Yes, muscle weighs more than fat. That much is true, so if the calories you consume are converted to fat, you will weigh LESS than if the calories you consume are converted to muscle. This is why when people begin a weight loss program that includes exercise; they often gain weight, even though they look thinner. (Muscle takes up less space than fat too). So again, there is no "extra mass" gained. By way of further explanation --- We are biologically designed to use food in the most effective manner. What we need we use, what we don’t need we store. When we go from being chip-eating couch potatoes to diet and exercise mavens, we change our body's priorities from storage to usage. When we exercise, fat is burned first. Fat is our biological storage unit for calories. It's where we "save food" for a rainy day. When sudden exercise kicks in, our body says "Whoa, I need more energy, better start drawing on the reserves." And we begin to burn fat. Also, as a separate process, when we exercise we build muscle because our body "notices" that we are now using our muscles so begins to send energy there. The muscles are built directly from the calories we consume. Again, we won't gain more than a pound of muscle for each pound of food we eat. In fact, it will be much less since it takes more energy (calories) to build muscle. When we exercised, the calories we ate "went to" the muscles instead of the fat because we are designed to send calories to the places in our bodies where we need them most. Muscles being exercised a lot need calories. If NO muscles are being used, and no other biological functions (such as pregnancy for example) require extra calories (beyond maintaining the body), then we just store them as fat. A brief aside on that topic, if we burn up all of our fat and then continue to burn more calories than we eat, our body begins to shut down non-essential functions and also begins to burn muscle mass. As we continue to deprive our body of energy, even essential systems shut down. This is the danger that anorexics face. Eventually the body just can't sustain itself. 3) When I lose weight, is the mass burned for fuel, and if not, what happens to it? If, by "mass" you mean the mass of the food, Yes, because we are talking about a calorie, a unit of heat or energy. When you lose weight it is because you have expended more energy than you consumed. This means that you have not only burned off all the food you just ate (by building muscle and running other bodily functions), you also drew from your reserves (fat). So yes, you "fuelled" your body with the mass you consumed. If you are talking about the mass of the fat we burn, the answer is still Yes. Our bodies "burn" calories through metabolic processes, by which enzymes break the carbohydrates (starches) into glucose and other sugars, the fats into glycerol and fatty acids and the proteins into amino acids. These molecules are then transported through the bloodstream to the cells, where they are either absorbed for immediate use or sent on to the final stage of metabolism in which they are reacted with oxygen to release their stored energy. It helps here to understand the concept of the calorie ---- Often the misconceptions about weight gain (and loss) are a result of people not understanding what we mean by a "calorie". They often think a calorie is a little "thing" that has to be gotten rid of. A calorie is a unit of energy (or heat). For food it defines how much energy is needed to burn of a unit measure of a particular food. For exercise it means how much energy your body is burning. So all this means is that the more calories a food *has* the more energy it takes to burn it up. Here are some useful links from which I drew some of the previous information --------- "…they think that, if you eat a pound of chocolate, you can gain more than a pound. I can't understand where the extra weight would come from." http://www.homestead.com/prosites-waynewatcher/Support_FatFact.html A pound is a pound and no more. http://www.myjanee.com/livelight/eat/weigh.htm Fat to Muscle http://shop.store.yahoo.com/homegym/fattomusrevb.html How is it possible to lose inches but not pounds? http://www.gymamerica.com/gti/magazine/magazine_qa/0,3291,1_cid_536,00.html What is a Calorie? http://www.howstuffworks.com/calorie1.htm How food works http://www.howstuffworks.com/food.htm The Caloric Concept of weight control http://nbaf.com/nbaf/feb7pgf.htm How your Metabolism Really Works http://www.metabolism.com/lifestyles/2001-05-22/ Metabolism - A primer http://www.mayo.edu/comm/mcs/news/news_1608.html I've put all of this in the simplest biological terms I could. The links should provide you with more in-depth discussion. If anything I've said is not clear, please feel free to ask for a clarification. Thanks for the great question - --K~ Search terms "eat a pound" weight gain "fat to muscle" "what is a calorie" "how we lose weight
"how metabolism works"
"If I eat a pound of butter, I gain more than a pound of fat, so where does the extra mass come from?" According to most sources, a pound of butter supplies 3200 calories
In order to gain a pound of body fat, you must consume 3500 calories.
I believe your answer is not correct. See the USDA Nutrient Database for Standard Reference http://www.nalusda.gov/fnic/cgi-bin/nut_search.pl Any of the oils contains roughly 123.7 Calories / .5 ounces or 14 grams 16 ounces in 1 lb 123 * 2 * 16 = 3936 calories 3500 calories in 1 lb of fat and for digestion / thermic effect of food roughly 3% of calories are used (fat is stored more effeciently then carbohydrates and protein) so we have a net gain of 3817.92 Calories which is more than enough for a pound of fat mass. The same can be said of lard and other very fatty foods. It seems that the weight is not the issue but rather the energy contained in the food.... the laws of thermodynamics are what comes into play.
Okay, so if I understood all of that right, I should just breathe, sweat
and pee more than usual and I'll lose lots of weight!
End of story!