Can you gain more weight than the food you ate weighs?

[coloradorudy]

It's agreed that 3500 calories is roughly equal to one pound (i.e. if you eat 3500 calories more than what your body requires, you will gain 1 pound). But 1 gram of pure fat (lard) has 9 calories. 453 grams per pound means that 1 pound of pure fat has 4077 calories. Thus, if you eat 1 pound of lard, you will gain MORE than one pound of weight (about 1.16).

This defies what I know about conservation of mass. What am I doing wrong?

[alextemplet]

Food's mass does not necessarily equal its calorie value. For example, sugars contain approximately one third the calories per gram of fat.

[mith]

*roughly* if you eat a pound of lard, it is not logical to believe that it would be converted back into fat cells. there's issues of digestion/absorption, lipid conversions etc etc

[biohazard]

A human body (or any other biological system) is not able to fully convert their diet (or the energy within it ) into body mass - so simply put, you cannot e.g. eat 1 kg of something and gain over 1 kg of mass. Solely the process of digestion and breaking down nutrients requires a fair bit of energy, and the overall efficiency of the human body is maybe ~25% - that is, 75% percent of the energy you consume is wasted anyway - and from that one quarter of "efficient" energy, a small portion is converted into tissues (=body mass).

About the only scenario when you can "gain" more weight than the food you ate is when you eat e.g. something very salty, which binds water, causes thirst and allows your body to retain more water than normally - thus your weight increasing more than your initial meal was. Of course, this is not real weight gain, just a temporary increase of the water bound in your body - the dry weight gain in your body tissues would still be considerably smaller than the (dry) weight of your meal.

Now, what comes to your calculations about ~3500 kcal being equal to one pound of body mass and so - it is a very simplified scenario, and - like mith said above - does not take into account of various factors in metabolism, composition of different tissues or the amount of water in that increase of body mass (which is likely to be something around 55 to 70% like the general water % of humans - and the amount of water in you has little to do with your energy intake, and more to do with the general body composition = muscle, some 75% water, fat tissue some 25% plus the gender differences et cetera).

Wow... this turned out to a long post, I should probably get me a few more hobbies