Jul 24 2009
Calories Revisited
I am a proponent of the notion that the dominant factor in determining weight gain or loss is the formula – calories in vs calorie out. In fact, this formula is inescapable – change in weight must be equal to the total calories consumed minus the total calories burned.
Whenever I write about this topic, however, angry critics (food is always highly emotional) charge that this formula is not true because it is too simplistic. But I think they misunderstand the formula. For example, some argue that this formula does not necessarily explain the differences among people. This is partly correct, but irrelevant. It does largely explain the difference – overweight and obesity does in fact correlate with higher caloric intake, and all weight loss diets work by reducing calories.
But, people are different – they have different digestive systems and different metabolisms. They have different amounts of brown fat – the kind of fat that burns calories to generate heat. Therefore, some people burn more calories while sitting and watching tv than other people, and they are more likely to be thin.
However, at present there is no safe and effective way to change people’s metabolisms. Without going into detail, I do not think that stimulants are a safe way to achieve this. And drugs to block food absorption have been pulled from the market due to side effects.
Therefore, while metabolism may explain why person A is thin and person B is overweight, if person B wants to become thin they need to either decrease their caloric intake and/or increase their caloric expenditure.
And keep in mind that the evidence suggests that most people who are overweight are so not because they are victims of their genetics, but because of their lifestyle. This is actually a good thing – because we can change our lifestyle. (This study shows that the morbidly obese are sedentary 99% of the time. Data shows that per capita food consumption is up 16% in the US since 1970. – just to give a couple examples. )
One of the simplest and most effective ways of altering behavior to consume fewer calories is keeping a food diary. Essentially, anything that makes us pay attention to how much food we are eating is likely to decrease how much food we are eating – which is probably why most diets work in the short term. It also makes sense that we should pay attention to the caloric density of the food we eat – an apple may be about the same volume as a slice of cheesecake, but their caloric content is not the same. We need some way to estimate the amount of calories that we consume, so that we do not accidentally over eat.
A recent article in the NewScientist points out that one barrier to accurate calorie estimating is that the number of calories reported on various food items may be misleading. Food calories are calculated using the Atwater system, which assumes that our body burning food for energy is literally equivalent to incinerating the food and measuring the heat produced. I remember seeing this on a “Mister Science” type show when I was a kid – burning a pile of jelly donuts and saying that the energy released is the same as if we ate the jelly donuts. Cool.
But there’s a catch – processing, digesting and absorbing nutrients from food costs calories, and some of the calories in food are consumed by the bacteria in our guts or excreted as waste. Therefore what we really want to know about the food we eat is not how many calories are in the food but how many calories we will net from eating it. If a piece of food has 100 calories, but it costs 20 calories to extract that energy, and 10 calories are lost to bacteria and stool, then we are only netting 70 calories from that piece of food.
If all food were 70% efficient then this would not be a big deal – in fact lowering the number of calories reported on food labels may contribute to more overeating. But the real issue is that different foods have significantly different efficiencies. Soft foods are easier to consume than hard foods. Cooked foods are easier to digest than raw foods. Cooking food actually gave a huge boost to human evolution because our ancestors could extract many more calories and nutrients from their food, and expand the number of foods they could eat.
Cooking is interesting because we are literally using energy from fire to replace energy we would have to expend in digestion, and we can get more energy from the food.
Differences in food calorie efficiency can range from 5-25%. Some argue that food labeling should reflect this – not just the total Atwater calories. Therefore we would be better able to estimate our caloric intake. At present people may falsely assume that soft and easily digested food is equivalent to mechanically hard and fibrous food of the same calories.
The differences between total and effective calories may also explain why highly processed food seems to be associated with being overweight. Processed food is not necessarily bad for you – it is just highly efficient. Finely milled wheat is more efficient than whole grain. Chopped or processed meat is more efficient than whole meat.
Efficiency was a good thing when we were scraping out a living in the wild. It is also a good thing in those parts of the developing world where hunger and starvation are a problem. But in the affluent West – we are victims of our own efficiency. If you want to lose weight, you want to be caloricly inefficient.
This one realization about effective calories vs Atwater calories is not going to solve our obesity problem. But each little bit helps. I maintain that the weight loss industry has been largely counterproductive – promising easy solutions and distracting people from the real issue. For any individual hoping to maintain a slimmer and more healthy weight, keep it simple. Find a fun exercise you can do on a regular basis. And keep some basic track of your effective calorie intake and keep it under control.
Calories in – calories out.
21 Responses to “Calories Revisited”
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I’m glad you mentioned the difference in efficiency for extracting calories from different foods! It is one of the things people often get wrong when talking about diet, and it tends to drive me nuts…
My roommate once went and got tested to see how many calories her body burns. She learned that if she limits herself to 1600 calories a day she loses weight. So she has been measuring what she eats. Literally, for every meal she gets out a scale, and a calculator and does what Steve suggests and keeps a food diary. And it works.
But, that only works because she got tested and knows how many calories her body uses. Just guessing doesn’t really seem to do it.
An easier way is to use the scale. Weigh yourself once a week. This provided end-point feedback that anyone can use to adjust their caloric intake to maintenance or weight loss or gain.
I suppose that would work too.
People have some strange ideas about calories. I have more than once heard someone say something like ” If I ate that piece of cake or 4oz candy bar I would gain 10 pounds”. When I quizzed them about this notion, I realized that they ‘literally’ believed that they could gain more weight from a food item that what it actually weighed. When I told them that they could eat a whole pound of sugar or chocolate and not gain even a full pound, they thought I had lost my mind.
tmac thats a good story, I be a lot of people probably think that way. But the grain of truth in that story is that no one ever eats just one candy bar. If you are the kind of person who eats candy bars, you are the kind of person who eats at least 3 or 4 a week.
My wife and I have been doing a “calorie diary” for the past 4 months, in addition to exercise 3-4 times a week, and have both lost 30+ lbs. It really does make a difference. The average portion at a lot of restaurants is just outrageous, calorie-wise. If you go to a place like Chili’s, most entrees end up being close to or over 2000 calories. And that’s not including appetizers or drinks.
One of the previous posters mentioned that knowing how many calories your body uses is important. Well, there are ways of approximating this amount:
http://weightloss.about.com/od/eatsmart/a/blcalintake.htm
If you own an iPhone there is a very nice app called LoseIt! that my wife and I have both been using to keep track of our calories and exercise. It even takes care of the “calorie budget” estimation for you.
Of course, calorie diaries, approximations of your daily caloric needs, etc. are not exact by any means… but, like Steven said, “anything that makes us pay attention to how much food we are eating is likely to decrease how much food we are eating”. Even though these methods aren’t precise, they do force one to pay attention what they consume and how often they exercise, and these are good things.
Don’t forget that some of the weight that one accumulates comes from air & water as well, not just the food…
I understood that low-carb diets worked on the principle of efficiency: digesting fats and proteins burns more calories than digesting carbohydrates. Is that correct?
Thank you for a clear and simple explanation of something I’ve seen discussed in a different context in the past.
And regardless of how efficient your food is at delivering calories, or what your matabolism is, the only sure fire way to lose weight is the one scientifically proven to work weight loss system (Weight Watchers, based on Richard Simmons): eat less and excercise more (and, if you’re Richard Simmons, feel good about yourself).
Anything else is just an excuse for being fat.
Correct, taustin, though I’d like to add that while anything else is just an excuse for being fat, this isn’t always the same thing as an excuse for being *lazy*, and there are actually some good excuses out there for certain people.
For most of us, they’re bad excuses, but there are folks, like my late aunt, who suffered from Addison’s Disease, for whom it’s a good excuse. Until the Addison’s was treated, she was unable to lose weight, and had a whole bunch of other nasty symptoms as well.
The calories in – calories out equation still works, even for folks like her, though. It’s just that the disease makes it so difficult to work the equation to your advantage, because your body becomes bound and determined to stash as much as it possibly can.
tfk, my understanding with the low-carb diets such as Atkins is that it’s mostly about inducing ketosis, a state that your body goes into when blood sugar levels are low and it responds by burning fat to supply the sugar your body needs to function. It does work, but takes a lot of work to achieve, and is potentially dangerous (ketosis is not a normal state, and the diet tends to lead to a lot of fat and protein consumption, raising risks for heart disease and gout). It really does work if you manage to stick with it, but I’d make sure your doctor knows what you’re doing so your condition can be monitored. (If nothing else, it’s liable to throw off tests for pre-diabetes, and you probably shouldn’t do it while you’re pregnant or trying to become pregnant.)
The idea of tweaking the efficiency of the foods you’re eating is of course an old one, and is the basic concept behind sugarfree pop and lowfat milk — removing some of the calories but leaving the same bulk. Weight Watchers has menus, and there are mail-order food outfits that arrange your diets with the express intention of keeping the same bulk (and, hopefully, flavor) with fewer useful calories. The old classics work well, though. Iceberg lettuce and raw celery stalks are great diet snacks because they have significant bulk but negligible useful calories. (Case in point: I used to keep an iguana. The guidebooks all tell you not to feed them iceberg lettuce under any circumstances, because they’ll starve to death on that diet. Spinach is good for them, though.) Of course, they’re also pretty bland. Most people cover them with ranch dressing, which rather defeats the purpose.
Ketosis is very likely completely incompatible with being pregnant or nursing. There is an obligate need for glucose to generate lactose for lactation and to supply the fetus with glucose for glycolysis. In rats there is a period during pregnancy where the absence of carbohydrate in the diet leads to insufficient fetal stores of glycogen at birth. This can very easily lead to brain damaging hypoglycemia shortly after birth.
Good job MercuryShadow, congrats.
I’ve lost 60+ lbs using the Weight Watchers (not that I’m trying to endorse that program) online food/exercise diary.
Dr. Novella is spot on with the calorie density thing. The only time I’ve even felt hungry was the first few weeks when I was still changing my eating habits. By eliminating the more calorie dense foods, I stay satisfied all the time. Yeah, it means eating several pieces of fruit or some carrots instead of the cheesecake, but if you’re trying to lose weight, it sure beats feeling hungry!
“And keep in mind that the evidence suggests that most people who are overweight are so not because they are victims of their genetics, but because of their lifestyle.”
I’ve always been sensitive to the fact that some people have a harder time losing weight than others, whether due to genetic diseases, depression, finances, having more pressing priorities, and so forth. I’ve never judged people for being fat.
However, at one point in my young adult life I did notice something interesting. When looking around at restaurants, the people eating salads and vegetable platters and Subway sandwiches are by and large skinnier, and the people eating fried chicken and gravy and hamburgers are by and large fatter.
This even applies to myself. I used to be skinny and a healthy eater, and now I’m drifting into worse food habits, and into being somewhat overweight.
Despite all the confouding circumstances, it really is lifestyle more often than not.
“However, at present there is no safe and effective way to change people’s metabolisms. Without going into detail, I do not think that stimulants are a safe way to achieve this. And drugs to block food absorption have been pulled from the market due to side effects.”
Precose(Tm)? It’s still available.
TurboCramb, I too lost 60 pounds way back in the late 90′s. But,
I think the five hours I spent at the gym daily was the reason for my success. Of course, I had a supportive sports masseuse to assist me weekly.
I was going to let this go, but since I’m going through the archives of the SGU podcast and the subject keeps coming up, and completely getting on my nerves…
Yes, while it IS as simple as move more, eat less, it just isn’t that EASY. I’ve been on every diet imaginable for 30 years and have a 100% failure rate. Willpower isn’t enough! Food is about more than supplying your body and not everyone can just “forget to eat.” I’ve never understood when people say that. Until recently, I was ALWAYS hungry and always on the verge of losing control.
Last November I finally got some chemical help for my anxiety and depression, and whaddya know, within three weeks I dropped six pounds without changing my “lifestyle” one bit. I didn’t start exercising and I didn’t purposely reduce my intake. I just quit obsessing about food and stuffing my face to soothe myself. Once I had some control I was able to continue successfully. Now I can get myself to stick to a healthier way of life, eating better and exercising regularly.
So what I mean, basically, is that while folks with 10 or maybe 30 pounds to lose might just be able to deal with the “easy” calories in/calories out method, it doesn’t work for everyone. Some of us need a little extra help…
A very astute article and great comments. I have to agree that it is indeed as simple as reducing calories and increasing activity (“eat less and move more”), as I have lost 100 lbs on the Weight Watchers regimen in the last year and a half doing just that. It has not been easy and there is indeed a lot of willpower that one must cultivate to achieve results, and I have little tolerance for those who profess to want to lose weight but refuse to make the necessary changes to make it happen (including the genetics excuse….my family is primarily overweight and I have been all my life too). I hardly eat any processed foods at all, mostly fresh veggies, fruits, whole grains and lean proteins which definitely keep the satiety factor up. It’s a shame that the diet industry focuses on quick fix solutions that will just lead to gaining it all back once the “diet” is over.
Se the following very interesting overview of glucose and fructose metabolism http://www.uctv.tv/search-details.aspx?showID=16717 . A written summary is given here http://www.ucsf.edu/science-cafe/articles/obesity-and-metabolic-syndrome-driven-by-fructose-sugar-diet .
Dr. Novella,
By way of introduction I am a nutrition science analyst. My interest is nutritional controversies.
My take on chronic disease in general and obesity in particular is that, over the past 3 decades, recommendations developed by the USDA’s Center for Nutrition Policy and Promotion (CNPP) have generated considerable confusion as to what constitutes proper nutrition. Specifically, advice to lower fat intake to lose weight and decrease saturated fat consumption to prevent clogged arteries has propmted the food manufacturing industry to develop an array of carbohydrate laden products containing unhealthy levels of omega-6 fatty acids, trans fats, and high fructose corn sweetener. Coupled with a relentless campaign to demonize animal fats, agribusiness and the food manufacturing industry have convinced Americans that red meat, eggs, and dairy fats are terribly unhealthy. At the same time, the CNPP’s dietary advice for Americans contained no strongly worded warnings about the hazards associated with excessive sugar and omega-6 vegetable oil consumption.
These four major mistakes in dietary advice need to be corrected before the food manufacturing industry will do much of anything to improve the quality of the ingredients in their products. Moreover, Americans will continue to consume foods that promote obesity until the quality of nutrition instruction in the schools and media is improved.
By the way, I got to this blog through a comment posted by someone critical of my viewpoint.
http://www.sciscoop.com/dietary-advice-and-obesity.html
Hi, Steven
“change in weight must be equal to the total calories consumed minus the total calories burned.”
This off course is correct, but you imply a causality, i.e. one chooses (or mistaken) to consume more, and -> you have a change in weight, while the causality might be reversed, i.e. due to hormonal or other malfunction, your adipose tissue take in a lot of the kcal’s as fat or has a difficulty to release it for consumption by the muscles between meals -> and then you are driven to be very hungry and consume more.
“(This study shows that the morbidly obese are sedentary 99% of the time. Data shows that per capita food consumption is up 16% in the US since 1970. – just to give a couple examples. )”
Obviously the obese are sedentary – they might have no energy at the cellular level due to defects in control over release of fatty acids to muscles, again the arrow of causality might be reversed (this is also known to anyone who dieted – you are cold and sedentary), if you assume this, than what all those “studies” do are simply document what other stuff is correlated with getting fat.
OK, consumption is up 16% – I really do not need a study to know this – you can directly see it by the girth of the people on the street – this is obvious, the question is why are people consuming more?, actually saying that people got fat because they ate more is saying the same twice, as Gary Taubes (from memory) said it, it is like saying that a room is full, because more people entered it than the number of people who left it.
What you imply that the control over weight stability is actually a conscious effort that need be more informed to be perfected – then the obesity epidemic will be conquered, and the only way people in history kept normal weight is because they were starved, I wonder, how my pets manage to stay lean without a food diary, while I give them unlimited portions.
Anyone who dieted successfully, knows that a time comes when the caloric deficit simply doesn’t seem to move the weight down, and if you go back to your previous weight stable calorie consumption – you gain weight, what does this say on kcal in/kcal-out?
“Efficiency was a good thing when we were scraping out a living in the wild. It is also a good thing in those parts of the developing world where hunger and starvation are a problem. But in the affluent West – we are victims of our own efficiency. If you want to lose weight, you want to be caloricly inefficient.”
When food is plentiful animals reproduce, not get obese diabetic and die (Gary Taubes, GCBC from memory). I do not think there is any reason to think people should have anymore difficulty maintaining weight than other animals.
“I maintain that the weight loss industry has been largely counterproductive – promising easy solutions and distracting people from the real issue.”
I think that the nutrition “science” was counterproductive by continuing to spread logical fallacies and continuing to research and document what stuff is correlated with obesity (been sedentary, larger portions etc..) instead of trying to understand the real physical causes of this terrible affliction – instead of maintaining it is purely psychological and either you are lazy, gluttonous or deluded and simply can’t count calories very well.
The weight lose industry developed because there are no results from the nutrition science – really no results at all.
“For any individual hoping to maintain a slimmer and more healthy weight, keep it simple. Find a fun exercise you can do on a regular basis. And keep some basic track of your effective calorie intake and keep it under control.”
This begs the question, why than while by all research and experience, it seems that this advice simply doesn’t work in the vast majority of cases, why, you all continue to spread it? how is that different from lets say … homeopathy? what are the scientific basis for this advice “eat-less move-more”, how is this not disseminating pseudo science? Does it work for you?