Are all calories equal when it comes to weight loss?

Suppose a pair of identical twins who have identical weight, percent fat is of body weight, etc. etc.

They decide to go on a diet to lose weight.

Twin 1 decides to go the healthy route and consumes 1200 calories a day composed entirely of lean protein and non-starchy vegetables.

Twin 2 decides that if he’s going to restrict his eating, at least he should be consuming what he wants. His diet is 1200 calories a day of Coca Cola and donuts.

Will they lose weight at the same rate?

In the short term, yes.

In the longer term, maybe not.

Bodies need x calories per day to function. If fewer than x are consumed then the body must burn its stored flesh. Usually, stored fat is burned first and then stored muscle. (Burned meaning broken down into the glucose that is the body’s standard energy source.) But at the same time, consumed food is broken down to basic components, which are then used to build up bodies. If you’re not taking in protein over the long run you need to get it from stores. That would throw off the ratio at which stores are used.

I don’t see any way to quantify the difference with this level of detail. I’m already using a pretty gross level of generalization.

The composition of the weight loss will be radically different between the two, even if the total pounds lost is similar. Without increasing protein along with overall calorie reduction, much more lean mass will be lost. So even though they have lost the same amount of weight, they look very different.

You didn’t specify that the twins would be equally active. I suspect a healthy diet would make it easier for Twin 1 to be active and burn calories.

Ok, “radically different” might be a stretch but “noticeably differrent” is definitely not.

Actually no.

It takes calories to process food and some foods take more calories to process than others, and some foods have the calories but the body does not completely use them.

This NYT quiz helps demonstrate how off listed calories can be between foods high in protein and/or fiber (diet one) and foods high in refined carbohydrates (diet two). Short version:

Note: the hypothetical excludes the impact that the diets would have on satiety, how likely it is that the listed calorie intake would not be cheated on, or at least how difficult it would be to do so, and the impact of the diets on activity levels (significant) and thus calories out, and on body composition. But in real world these differences, already alluded to in responses given, would be significant as well.

The biggest difference between different sources of Calories is how easy it is to stay on the weight-loss regimen (which should include both diet and exercise). Of course, how easy different regimens will be will vary widely from person to person, which is why there are so many different diet plans out there.

I think not, but I don’t think it has been carefully enough studied to be certain. For one thing, as mentioned above, different foods may be digested differently. Case in point: you can eat carrots raw or cooked. The official calorie content is the same, but the difficulty of extracting those calories will differ markedly. Complex carbohydrates are harder to digest than sugar and might not be digested as completely. But absent careful studies, who knows.

I made the hypothetical as radical as I did so that whatever impact there might be on weight loss would be maximized. I do think the twin on the Coke and donut diet would not feel satisfied and would likely cheat – 1200 calories doesn’t buy you many cans of Coke and donuts. But having been on a diet composed primarily of lean protein and low-carb veggies, I can attest it’s not all that easy to stay on, either.

I find the differences in calories actually used by the body to be fascinating. Is there any way for research to give accurate estimates of how many calories are used, or is this too individualized?

I remember reading some years ago that when you eat foods that are very high in fiber, it’s not only the high-fiber food that has fewer calories used than other foods, but the high-fiber food can “push” other foods eaten through the digestive system faster and therefore the calories used in those foods are lower, too.

Perhaps (actually, I think “probably”) this has been debunked. But speaking from personal experience, if it is true in general, it may not be true for me. Because even when I eat a very high fiber diet I still have issues with constipation.

1200 Calories is about 1 can of coke plus 3.5 glazed donuts. That only gives you 11 grams of protein. I’m not sure one could survive on that.

The thermic effect of food is highest in protein:

Thanks all for the answers!

Does this mean that the Atkins diet (and other diets which restrict simple carbs) are more effective in fat loss than traditional diets which focus on restricting calories?

Also, I have heard that low-carb diets aren’t as effective in weight loss the second (or third or whatever) time around. That is, someone loses significant weight on a low-card regime, goes off the diet and puts the weight back on (of course, this lose-weight-gain-it-back cycle is true of all diets), and then goes back on the low-carb diet. But this time the weight doesn’t come off as quickly. Is this in general how it works? If so, any data on why?

Too, I have heard that people who lose weight on a low-carb diet and then go off the diet, put on weight faster than those who lost the weight on a calorie-restricted but not low-carb diet. That is, my hypothetical twins blow their diets big time and spend a few weeks eating 3000 calories a day that includes a lot of sugar and other simple carbs. Will the twin who lost weight on the low-carb diet gain weight more quickly than the other twin?

I have also heard that on very low-carb diets, your body goes into something called ketosis (I think) that causes you to lose weight more quickly. However, if you consume even one food or beverage high in simple carbs, it takes you out of ketosis and derails your weight loss for not just that meal but for several other meals. True?

If one loses fat while on Atkins, it’s for the same reason as any other diet: that person is consistently in a caloric deficit. The diet that is the most effective is the diet one sticks with and adheres to properly. Protein (for most people) is the most satiating of the macronutrients, so higher protein levels help with dietary adherence. A quick YouTube video featuring my favorite nutritionist:

[quote] I have also heard that on very low-carb diets, your body goes into something called ketosis (I think) that causes you to lose weight more quickly. However, if you consume even one food or beverage high in simple carbs, it takes you out of ketosis and derails your weight loss for not just that meal but for several other meals. True? [/QUOTE]

The following is educational:

Carrots are discouraged as a snack in many diets because they have a high glycemic index (they raise your blood sugar very quickly). This has been criticised because the index was determined on cooked carrots, and who has cooked carrots as a snack?

Regarding the importance of glycemic index (yes, it’s an article in a pop exercise magazine, but the author really knows his stuff):

My two cents…

The biggest problem with “dieting to lose weight” is that it’s a flawed concept from the get-go and anyone who does it is asking for failure.

Your body composition is determined by your genetics and your lifestyle. You can’t simplify that and there are no shortcuts. Since you can’t change your genetics, the only part of the formula that you can change is your lifestyle. That means not only what and how much you eat, but how active you are.

The problem is that changing your lifestyle is incredibly difficult - it fact, it’s so difficult that the vast majority of people simply can’t do it.

The only “diet” that makes any sense is a well balanced diet of mostly fresh foods, with highly processed, calorie dense foods kept to a minimum.

No one should ever “diet to lose weight.” You need to change your lifestyle so that your body composition adjusts to where you want it to be. The “diet” you eat “to lose weight” should be the permanent healthy maintenance diet for the body composition you want. You don’t “diet down” to a certain weight and then switch diets. You simply start eating the best diet you can and adjust your total daily calories as needed to fit your lifestyle.

From personal experience, I can tell you that controlling weight through diet alone is a fool’s game.

You metabolism will just slow down until you feel like shit and decide that dieting sucks.

Unless you’re one of those"I can eat anything and still look great" people, then sorry to say it, but a healthy body composition is only going to be the the result of a healthy lifestyle and there’s really no getting around that.

If you want to change how you look, you have to change how you live your life, not just change what you eat for a short time.

Not so. Even raw carrots have a high Glycemic Index because the Glycemic Index is calculated based on the number of grams of carbohydrate in a particular food rather than the total quantity of food itself, and carrots are quite low in carbohydrates.

Raw carrots have a high Glycemic Index but they have a very low Glycemic Load.

IIRC - The theory of the Atkins diet was that the “I’m starving, better burn that fat” trigger is separate from the trigger that causes the body to go into starvation mode, shut down as much as possible and start consuming the muscle mass to minimize calorie burning.

The former is triggered by a lack of carbs - so an almost zero carb diet will cause the body to burn fat (ketosis?) while eating a decent amount of protein (and fat) will prevent the full starvation reflex.

Like any discussion of diets and weight loss, it’s impossible to say what is urban legend and what works (and why). My anecdotal experience (which proves nothing) is that I went from 235 to 208 in 3 weeks, and put it all back on again fairly quickly once I stopped watching carefully what I ate.

Was this study fair in giving the “low-carb” dieter 33 grams of carbs when Atkins specifies a maximum of 25 carbs per day? Also, the author refers to it as a “ketogenic low-carb” diet, but did he do any blood tests to determine the participants were in ketosis?

That’s an understatement of the Atkins carbohydrate limitations. During the first two week induction phase carbohydrates are limited to 20 grams per day. In the ongoing weight loss phase you add five grams per day every week until you stop losing weight, than you subtract 5 grams per day and hold that level. There’s a pre-maintenance phase where you add 10 grams per day per week and a lifetime maintenance phase as well. Everything except induction allows more than 25 grams of carbohydrates per day.