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

*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

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 😉

The question seems to be can you gain more mass than you take in? Obviously not.

But you take in mass as food, drink and respiration.

Similarly, you chow down with solids and liquids, and the ability to gain weight is determined by how much of that total is retained, plus the weight of any oxygen you breathe in (and some small measure of nitrogen) that becomes chemically altered into body mass.

What chemical scenario, at the molecular level, might turn a pound of food solids, a pound of oxygen, a 1/16 pound of hydrogen (much of the last two from the water in beer in my case), and a smidge of nitrogen, minus half a pound of carbon into more than a pound of belly roll?

Or in more practical terms, can you gain more than an ounce of body from an ounce of cheese, given all the metabolic factors?

It’s not the energy you might convert to mass (too relativistic for me) but the energy-carrying atoms and molecules that your physique might pack away as chains of proteins, sugars and cell structures after ripping apart the food and drink and water and respired oxygen and reassembling those "for later use."

I don’t know of an energy/reaction/chemical path that is that efficient. But I see an opportunity there to get close.

So here’s a different question. How MUCH of an optimum food can be retained without being simple water swelling?

What’s the record?

What’s seems wrong is not accounting for calories burned by not even doing anything. Just eating the lard burns calories. It seems like it’s like the calculation for power out = power in – friction. Your calories burned is like the friction.

I’ve never seen the 3500 calorie number but I would guess that it’s from some diet book or diet guru. That number does seem low for gaining one pound but like others said it all depends on what the actual food was. There are a lot of factors that go into how many calories you burn, energy you use and how much energy you store. I would be curious to know an average of how many calories it takes to gain a pound and how many carbs and proteins and fat the food contains.

Well i think it depends upon the concentration of starch and fat on the food. Sea food contain the same meat as chicken( taste the same too) but it has lesser fat. And that means it well help you control weight…..

Yes, food mass cannot be directly converted to how much body mass it gives. You can take the same amount of calorie from different types of foods and see varied result.

"35 calories is equal to 1 pound". It depends on the food item, your metabolic rate and other factors.

I think it greatly depends on the food you it and the fats it stores. Consuming i kilo of pork meet for example gives as much as 2x more fat than a fish fit with the same weight. 😉

Doc: nice, but how does that relate to whether you can gain more weight than the food you ate weights?

The simple answer would appear to be NO, you cannot gain more than the weight of the food you eat. Even if the food is salty and "binds" water in your body, either that water is already in your body contributing to your existing weight, and so no net gain; or you have to drink additional water, which is added to the weight of the food you eat. Even if you absorb some nominal amount of water by breathing (and I can’t believe that’s a significant amount, as you’ll perish of dehydration if you don’t drink fluid — breathing in even humid air won’t sustain you). So, unless the principal of conservation of mass has been discredited, you cannot gain more than the weight of your food (and liquid) intake. If you stand on a scale after eating (and drinking) all you will, you will not see your weight increase unless/until you resume eating.

^ Amen.