If you eat a 57 gram Snickers bar it is impossible to put on more than 57 grams of weight. I'm not really sure what you're looking for here.

Most of the cabbage will be water and fibers your gut can't process, whereas a Snickers bar is concentrated fat and sugar.

Right, but a single Snickers bar would net more bodyweight than a single head of cabbage is my point, because the Snickers bar is higher in calories, which means that the starting weight of the pre-consumed food is not indicative of weight gain. So how is that weight being actualized during the digestive process?

The cabbage has a lot of fibre that will pass through you (although this is good for your gut), and water as well that you'll just pee out.

You don't gain the weight of what you eat anyway. You need to process and digest it, which uses energy, and your body uses energy to heat itself, do basic processes, keep your brain running, etc.

Per gram, each macro (fat, carb, protein) has a different calorie value. It's based on how easy it is for your body to break it down and use the components as energy. Calories are just energy.

The macros/foods might have other properties. Protein is also used for muscle building and repair.

Calories are the unit of measuring heat energy. You should actually light a peanut on fire and light a dried piece of cabbage on fire.

Which one burns hotter, brighter, longer? This is actually the test they do in the lab to figure out calories, using a device called a bomb calorimeter.

It's chemical energy just like gasoline in your car. Not all gas is the same octane.

You're forgetting that your body changes those dry sugars into fat by adding water, so if you were dehydrated, you wouldn't put on the fat either - Though you could die from dehydration, so don't do that either. Your body is basically always 55-60% water, so if you're very heavy, you're storing a lot of water as well.

You're asking why some things contain more energy (that you can extract) than others?

Time to look up the Krebs cycle and oxidative phosphorylation. I'm sure they've been explained in detail on this sub before, and good old wikipedia will probably do a decent job of it too.

If I burn 100kg of rocks and 100kg of coal, which one makes you warmer?

The energy your body doesn't use gets stored as fat. Eating high energy foods results in more more fat.

That fat is stored in fat cells, which also contain a lot of water.

Conversely, the cabbage doesn't have a lot of energy, and most of its mass is water.

You can’t eat 1000 heads of cabbage in one sitting. Your stomach would rupture and you would die. You have to poop it out first.

Cabbage is mostly water and fiber. Your body can’t digest fiber, so you don’t get anything out of it (other than it giving your intestines a good cleaning scrape on its way out). You don’t get fat from cabbage, because virtually 100% of it just goes right into the toilet.

A Snickers bar has lots of delicious fats and sugars in it. Your body can use that. If you eat more calories than you use with exercise, then you gain fat. Since your body thinks you are a caveman who needs to store fat to survive times of drought and famine, instead of a lazy fatass with a thousand Snickers bars, it stores as much of that energy as possible. It converts it into fat. A lot of it will still come out as poop, but your body can retain much more of the Snickers bar than it can the cabbage.

Add a third item for comparison - a 1 kg bottle of water. That weighs more than either the Snickers bar or cabbage, but it's clear why you won't gain any weight from drinking the water (assuming you weren't dehydrated and you've had a chance to piss it out) - there's nothing in the water your body can use for energy now or convert to something it can store and use for energy later. The water just passes through you.

The bulk of the cabbage passes through you too because it's over 90% water. Most of the rest is insoluble fiber that just passes through our digestive system unused. Take away the water and the insoluble fiber, and you're left with a tiny bit of actual usable nutrients, and only some of that is potentially storable by the body.

A Snickers bar is about 6% water, and the bulk of the remaining 94% is calorie dense fat and carbohydrates (with a bit of protein). The body uses some of that for immediate energy and stores almost all of the rest, resulting in weight gain.

This is the general reason why vegetables seldom lead to weight gain - they're mostly water and whatever is left isn't terribly calorie dense(ignoring starchy veggies like potatoes and fatty veggies like avocado for the moment). Doesn't mean you can't gain weight eating only veggies, but it's much harder to do compared to eating more calorically-dense foods.

>Being much more calorie-dense, the Snickers bar would naturally result in greater weight gain

The weight you gain by eating isn't based on the weight of the food, but the calorie content. It seems like you get this concept.

The four macro nutrients in food are water, fat, carbs, and protein. However, water doesn't provide any calories for you to use. If you remove all the water from both foods, the Snickers bar is actually heavier than the cabbage.

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A weight gain of 47 pounds in a year is huge, yet it is only 2oz gain per day. 2oz is about 1/30th of your intake. So, it's not the mass of what you eat, it is the parts you retain

Most of cabbage is cellulose, which we tend to call fibre. Our bodies can't digest it so it passes through our system and is pooped out.

Chocolate bars are high in sugar and fat, things our bodies absorb very well so, all other things being equal, you retain far more mass from the chocolate bar than from the cabbage.

How much cabbage mass would come out as farts.