Calories and weight gain/loss

Right, I know that to lose a pound of weight, I roughly need to burn 3500 calories.

Does this mean if I eat 3500 calories worth of food (on top of the calories for metabolism, movement etc…) I would put on a pound?

What would happen if I ate that many calories of a food that has a very high calorie to weight ratio, where 3500 calories is less that a pound?

Cheers in advance,

It’s not a perfect correlation, but it’s pretty close. If you eat an additional 3500 calories over what you are burning off you will gain about a pound.

Fats are 9 calories per gram. There are 454 grams per pound. If you eat a full pound of fat, that’s 4086 calories. What will happen? Probably you’d throw up. Otherwise you’d gain 1 and 1/7 pounds.

What would the extra 2 and 1/4 ounces be made out of?

unregurgitated vomit, apparently.

You’re not just eating caloric solids, you’re also consuming liquids that contain a lot of water. When your extra calories find their way into fat cells, some of the water does too.

Fat. Your body doesn’t care how much weight was in the original food. All it cares about is the energy produced by the digestion products as they are used by the body. If those come to a gross 4000 calories the body will use or store 4000 calories. Don’t let the pounds to calories ratio mislead you.

It doesn’t matter what kind of food you eat or what the calories per pound of the food is. What you end up with is an additional pound OF YOU, not of the food you ate, for roughtly every extra 3500 calories.

Whether you ate a food with a high calorie to weight ratio, like a chocolate bar, or a low calorie to weight ratio, like cabbage, once the calories are onboard, they turn into a pound OF YOU, usually as a pound of body fat.

The mass of the food that isn’t calories will pass harmlessly through you.

(or what Exapno Mapcase said)

How is that possible? My body can take 1 pound of fat and turn it into 1 1/7 pounds of fat?

The extra weight has to be something else. I think panache45 probably has the right answer.

To clarify: the fat that you eat doesn’t go directly to your belly or your butt as fat. Like everything else you eat, it has to go through a complex metabolic process, before it becomes fat, or muscle, or waste, or whatever. You have to eat a lot more than a pound of food in order to produce a pound of fat.

That was my point. Fat calories are determined by burning the fat in a bomb calorimeter. It’s a very efficient process. In the body it’s less so. Say you eat a pound of butter. The butterfat doesn’t deposit directly into your ass. It’s broken down into glycerol and fatty acids which are then converted to human fat. There’s some energy loss along each step of the process. You can not gain 1 and 1/7 pound by eating a pound of anything. Around this message board we obey the laws of thermodynamics.

If you are just looking to lose weight, lose a pound of muscle; it’s much easier. Muscle has about half the calories by weight as fat. As a matter of fact, one of the mistakes many folks make is to lose weight when what they meant to lose was fat. The body has an unfortunate preference for consuming muscle and keeping fat in reserve, so folks who hop on a scale to see how their diet is coming along are often tracking the wrong parameter.

Restricting caloric intake will eventually cause your metabolism to switch over to ketosis, of course…

On the eating side, it’s not that simple, either. Exapno Mapcase’s explanation to the contrary, there isn’t some straightforward stoichiometric equation between what you swallow and what happens to your weight. This is because such simplifications ignore what you defecate out. And it turns out that is highly variable and markedly influenced by what you eat and even what your body is used to being fed. Give your dog a pound of butter and you can do a little personal experiment yourself (I’d let the mutt run around outside til he finishes crapping out the butter if I were you). Further, metabolism changes based on diet and the body’s homeostatic perception of caloric balance.

Finally, of course, how you are wired genetically is a huge contributor to what happens when you ingest an excess of calories. That’s why some people desperate to gain weight never do, despite their best efforts at eating more. Sure, eating more will help them gain more weight than if they eat less, but it’s not as if they can decide to eat 15 additional fat pounds of calories over two weeks and somehow gain those 15 pounds they wanted.

At a cellular level, it is much closer to a simple equation of calories in and calories stored. At an eating level, it’s not, which is why diet theories abound–each with their little kernel of truth, but almost all missing the bigger picture.

In Scientific American about a year and a half ago, Marion Nestle, leading America nutrition “expert” wrote that if you cut your calorie consumption by 500 calories a day, you will lose a pund a week.

Bull. If I cut my consumption by 500 calories a day, I will sit in a corner feeling miserable, wearing glove and two sweaters and shivering constantly. And I won’t lose a pound a week. This is one of America’s leading nutritionist and I am certain she has no actual data to back it up.

On the other hand, if I splurge on a big meal one evening, I will spend the night feeling hot and I doubt I will gain more than a slight amount. Digestion also extracts a price and none of this is counted.

Now if I decreased consumption by 100 calories a day for five weeks or, even better, 50 calories a day for 10 weeks, I might well lose a pound. I wonder whether any of this has actually been tested.

I was doing the thought experiment of ingesting pure calories. Of course real food contains water and indigestible fibers in highly varying amounts. That’s why I excluded real food from the discussion.

When it comes to the portion of food that contains actual digestible molecules - fats, carbohydrates, proteins, and sugar alcohols - the body is, as I said, remarkably efficient in extracting virtually all recoverable calories. You can sometimes see unchewed and therefore undigested food (corn, peas) emerge in the waste, and those who are lactose intolerant will have lactose proceed on to the colon, but otherwise most calories are taken out of the food consumed.

Yes, in the real world a pound of food does not make a pound of flesh. However, that’s not what the OP asked. The question was phrased - correctly - in terms of calories ingested. I can’t stop you from hijacking the thread but at least make sure everyone understands you’re answering a wholly different question.

(Bolding mine)

I’d be interested in learning the source of this information. I’m not a expert of any kind in this area, but my general impression is that the efficiency of caloric extraction from food varies significantly among individuals, and within individuals, varies with respect to what is being eaten. Among factors that can affect how many potential calories are extracted are factors which affect transit time, how well various digestive chemicals and enzymes are produced in a given individual (things like stomach acid, bile and pancreatic and other enzymes) and perhaps most remarkably, even the gut microbial environment. For example, one line of research into the cause of obesity looks at gut flora as a potentially significant contributor to what actually happens to food when it is eaten. (See here, for instance: DEFINE_ME

It’s not clear to me why my original reply might be construed as a hijack to this question in the OP: *“Does this mean if I eat 3500 calories worth of food (on top of the calories for metabolism, movement etc…) I would put on a pound?” *but if I misconstrued the question, I apologize. My impression remains that it is a common misperception that whatever you eat is pretty much all absorbed with high efficiency and that therefore fat people must be eating an equivalent amount more than thinner people to account for their obesity. It’s much more complicated than that. And as nearly any animal husbandry researcher can tell you, it’s reasonably common to breed fish and mammals with an eye toward selecting out for higher food-to-weight conversion precisely because there is so much natural variability…

We are fat because we eat too much and eat too much of the wrong things. But it does not follow that we convert what we eat into body weight (less calories expended) at anything close to near-perfect efficiency.

Just recently I almost started a thread asking about the caloric content of human poop, because of just this gap in the metabolism equation, but decided against it for reasons of… taste. But now that the topic has been breached, is there any ballpark figure, or percentage loss typical to various sources?

Why would you not lose a pound? Assuming you are currently eating exactly the right amount of calories to maintain your weight, I don’t see how decreasing your intake wouldn’t cause you to lose weight.

Hari, I am doing exactly that, reducing my intake by 500 calories a day. I count everything as best I can with an online calorie calculator, and allow myself 1200 calories a day of food. Then I exercise for about 300-400 calories worth each day (also calculated carefully.) My daily needs to maintain are about 1600 - 1700 per day, so I reward my exercise with allowing myself to eat about the same extra calories as I exercise, and I am losing pretty much exactly a pound a week. 25 pounds in 24 weeks so far.

For me, it is a very simple calories in/calories out equation. Just bloody hard to put into practice and keep on with!


But by your own computation you should be losing a pound every 4 days (500 calories less of food + 300-400 calories of exercising makes, say 850 calories a day).

Somewhat relevant to this whole thread is something I read a long time ago. The prevalance of starlings in cities is way down since the disappearance of horses from cities since undigested oats in their feces were a major source of food for them.

Anyway, my basic point was that once my metabolism goes into starvation mode, all these computations go out the window. Does anyone think I would shrink to nothing if I kept up such a diet indefinitely?

No, if you read what I said, I eat the same number of calories that I exercise to keep the deficit at 500.