It is of course different. Carbohydrates, protein and fat all undergo different metabolic pathways. Further down you are wondering why you might not have a high karma on this post. I think it's because what you have written conflates 2 issues (I suspect, though, that you aren't actually conflating them... just your writing is unclear).
500 calories from whatever source is 500 calories, when we are talking about energy. It is definitely possible for people to excrete excess calories, but if for example you are excreting a lot of fat, you will know about it. It is not pleasant. There are a fair number of people who are unfortunately misinformed and think that somehow they have super digestion for carbohydrates for example. They think they can extract 1000 calories from 500 calories of carbohydrates. This is impossible and it's why it's important to understand that from that standpoint a calorie is a calorie.
Of course nutritionally they are very different things. They are digested differently, at different speeds and metabolically burned in completely different ways. Different foods also have different nutrients and it is important to make sure that you get these nutrients. You can go an awfully long time without any symptoms being malnourished only to eventually come to a very serious problem.
So many people are (for lack of a better word) arrogant in their beliefs about nutrition. However, we still know very little about how our body works. Traditional diets have a long track history with many, many people. We have a good idea about potential nutritional problems and how to counteract them.
I was vegan for many years (although, strangely, not ethically vegan -- I just enjoy eating that kind of food). I have seen many invented diets cause serious problems and eventually I spent considerable effort to learn about traditional vegan diets. I'll caution you that the current attitude of "You can just cut out carbohydrates from your diet and be healthier" is unlikely to be true. Nutrition is complicated and can't be boiled down to something so simple. There are many shapes of diets that can be healthy but seemingly insignificant changes can take their toll on your long term health. Please exercise caution.
> I'll caution you that the current attitude of "You can just cut out carbohydrates from your diet and be healthier" is unlikely to be true.
I have a lot of sympathy for your conservative and skeptical stance in general.
I am glad though, that a lot of people have done the self-experimenting (that we probably wouldn't do to normal experimental subjects) and gone on a low carb diet.
They seem fine.
There are also some better monitored people on a low carb diet, eg for some kids with epilepsy it's the only thing that works. The kids main problem is usually getting enough calories, but not any lack of other nutrients. (I think the go to source of extra calories is coconut oil, because the kids seem to mind that the least.)
Edit: just checked the article above. Looks like they need to add multivitamins etc. Poor kid: his diet needs to be much more extreme than eg Atkins diet to keep the epilepsy at bay.
Mikekchar, "500 calories is 500 calories" is a tautology and neither a clever writing device nor a serious argument.
I've cut carbs out of my diet a few months ago, after I chewed through the 200-pound mark. I noticed I had trouble running, walking and even standing. I dropped bread, pasta and refined sugar, though I still eat fruits without restriction.
The result is that I've been steadily losing weight and shedding fat, primarily the nasty layers found in the pubic area.
My research has thoroughly convinced me that carbless diet makes the body burn fat and serves as a protective factor against neurodegenerative diseases.
I'm glad you are losing weight (if that's what you are trying to do). However, when you change your diet comprehensively it is easy to overlook changes. For example, did you seriously measure your caloric intake before and after you changed your diet? Are you sure that you did not overlook sources of calories?
I helped a friend of mine lose weight once. His original diet consisted of a single muffin and coffee for breakfast, a subway sandwich with iced tea and one of those tiny bags of potato chips that come with the meal, and for dinner some salad and spaghetti or something. It sounds reasonable, but for the life of him he couldn't get under 220 lbs.
We went through the numbers. The muffin he was eating was 500 calories! The chips, 150 calories. The salad dressing he was eating on his salad was over 100 calories. The ice tea was 180 calories. So that's 930 calories, or nearly 1/2 of his daily requirements in just those 4 items of food.
We made a few minor substitutions to his diet (which actually increased the volume of food he was eating) and he started running 2 miles a day with me at lunch (which is worth about 200 calories a day). He was down to 160 pounds in no time. Our biggest problem was trying to make sure he didn't lose more than 2 lbs a week because that can be hard on your liver.
The thing is, if he had gone on a no carb diet and found alternatives in his diet he probably would have had the same result. No muffin. No potato chips. No ice tea. Probably substitute the salad for something with more protein.
Like I said, I'm happy if its working for you. I know a lot of people on low carb diets. Every single one of them is overweight. I have yet to meet even a single person in real life for who this strategy has worked. Mostly I see people change their diet, lose some weight when they eat more healthily and then gain it back when they mistakenly think that as long as they keep out the dreaded carbs, then they can eat whatever the heck they like without consequences.
500 calories from whatever source is 500 calories, when we are talking about energy. It is definitely possible for people to excrete excess calories, but if for example you are excreting a lot of fat, you will know about it. It is not pleasant. There are a fair number of people who are unfortunately misinformed and think that somehow they have super digestion for carbohydrates for example. They think they can extract 1000 calories from 500 calories of carbohydrates. This is impossible and it's why it's important to understand that from that standpoint a calorie is a calorie.
Of course nutritionally they are very different things. They are digested differently, at different speeds and metabolically burned in completely different ways. Different foods also have different nutrients and it is important to make sure that you get these nutrients. You can go an awfully long time without any symptoms being malnourished only to eventually come to a very serious problem.
So many people are (for lack of a better word) arrogant in their beliefs about nutrition. However, we still know very little about how our body works. Traditional diets have a long track history with many, many people. We have a good idea about potential nutritional problems and how to counteract them.
I was vegan for many years (although, strangely, not ethically vegan -- I just enjoy eating that kind of food). I have seen many invented diets cause serious problems and eventually I spent considerable effort to learn about traditional vegan diets. I'll caution you that the current attitude of "You can just cut out carbohydrates from your diet and be healthier" is unlikely to be true. Nutrition is complicated and can't be boiled down to something so simple. There are many shapes of diets that can be healthy but seemingly insignificant changes can take their toll on your long term health. Please exercise caution.