Posted on 10 May 2012 21:17
Turning over a new leaf, just for this post, at least, I decided to actually write about fat loss. People who read my articles regularly know that I do not hand out weight loss advice. But a fun subject, and one a knowledgeable feller like myself can tackle, is the "negative calorie" claim that has surfaced through the years. The thing about this claim is that it can seem logical at first glance, to someone with no in-depth knowledge of nutrition, and at the heart of it, there is a kernel of truth. For those without knowledge and those who wish to cash in on that market, a kernel of truth is all that is needed.
Negative Calories and TEF
Negative Calories has to top the list of magical weight loss myths, because it would be the most amazing if it were true. This myth says that there are some foods that by virtue of their composition require more energy to chew and digest than they actually impart to the body, thus giving "negative calories" and helping to lose fat. Basically, you are burning calories by eating the food, so if you eat a lot of it, you'll lose weight!
It is actually pretty hard to believe, at present, that people swallowed this one, but they did. Oh, they really did! Celery was the king of negative calories. Other contenders are cabbage, lettuce, cucumbers, and Snicker bars.
But I did say there was a kernel of truth, didn't I? Well the idea is based on what is called the thermic effect of food (TEF). Of course, when someone comes up with a term like that, someone else always has to one-up them so there are other names for it like diet-induced thermogenesis (DIT), specific dynamic effect (SDE) of food, and specific dynamic activity (SDA) of food. You'll understand if I stick to thermic effect or "TEF" for short.
TEF is one of the three categories that total energy expenditure (TEE) is broken down into. The other two are your resting energy expenditure(REE) and your physical activity. You may also have heard the terms "basal energy expenditure" (BEE) or "basal metabolism rate" (BMR). See the section I added below for further explanation. For now, know that resting energy expenditure typically accounts for about 50 to 70 percent of TEE. Physical activity accounts for about 20 percent. That leaves just around 10 percent for the TEF. 1,2 In clinical settings, TEF is not measured, but rather estimated based on the equation:
TEE = (REE + EEPA) x 1.10
Again, TEE is total energy expenditure, REE is resting energy expenditure and EEPA is energy expended in physical activity, which includes both voluntary activity, such as exercise and activities of daily living, and the energy expended in non-exercise activity thermogenesis, or NEAT. And the factor of 1.10 accounts for the TEF.2
The TEF is the energy required to process the food you eat. It takes some energy to chew it, digest it, transport it, absorb it, metabolize its nutrients, and to store some nutrients. You chew food. That takes a bit of energy. The muscles in your GI tract speed up their contractions, so that takes some energy. Digestive juices and enzymes are secreted, and that takes some energy as well.3 All this produces heat, thus a "thermic effect". To produce heat is to expend calories.
The thermic effect of food actually has another component. The energy required to process the food, as I've described above, is called the obligatory thermogenesis. The other component is facultative thermogenesis. This is the excess energy expended above the obligatory thermogenesis due to metabolic inefficiency. 2
This COSMED device is an indirect calorimetry device.
Indirect calorimetry is a way of estimating energy expenditure in
steady state conditions from the rate of oxygen consumption (Vo2),
and the rate of carbon dioxide production (Vco2).
Image courtesy of COSMED
So how much energy are we talking about, for the thermic effect? Well it's easily overestimated. Or even underestimated. That's the problem. See, we can only estimate it in the first place and the errors involved in that estimate are likely so large that they offset any small contribution to calories burned. As you can see, it is simply assumed to be 10% and only the resting and physical energy requirements are measured actively. The composition of the diet greatly affects the TEF. The TEF is greater with carbohydrate and protein ingestion than for fat, protein being the greatest. It should be noted that this energy cost is probably more related to the cost of storage than to the cost of processing and absorption, although there are probably other components as well.
Also, other dietary factors such as spicy foods, caffeine, and nicotine can increase it. So based on our ten percent, let's say that a person who takes in 2000 calories a day burns around 200 calories to process the food….plus or minus how much?2,3
Looking at celery, you can see, as with many myths, there is an element of truth at base. Celery is 95% water and the rest mostly cellulose, which is difficult for our body to break down. One stalk contains only six to ten calories. The chewing part, well, that couldn't possibly burn enough calories as you'd have to chew for an hour to burn 5 to 10 calories, at an estimate. Which means an hour worth of celery. The math is a bit staggering to me so I'll leave that alone. The actual digestion? Sure, by the time the body deals with celery it is probably fair to say that there is no appreciable net gain in calorie energy. If you did nothing but chew on celery all day..you may even end up with a calorie deficit. But of course, you would never do that and there is no way you could ever eat enough celery to make a difference in your caloric intake. Celery is not only hard to digest, it is a nutritional pauper. A celery diet would be a diet with an absolute lack of proper nutrition.
The whole concept of a "negative calorie" is absurd in the first place. A calorie, by which we usually mean a kilocalorie, is a distinct positive value: the quantity of heat needed to raise the temperature of 1 kg of water from 0 to 1°C. There can never be a negative calorie.
Although most of the negative calorie hoopla is limited to advertisements or articles in questionable publications like the Weekly World News, it finds its way into mainstream books, magazines, and websites all the time. Negative calorie foods are often billed as foods that help you or even cause you to lose weight. Some M.D. named Neal D. Barnard actually wrote a book called Foods that Cause You To Lose Weight: The Negative Calorie Effect. 4
There is something called a Negative Calorie Diet but I am not sure if that is one fad diet, several, or just a general term for any diet claiming to utilize this effect. I really do not think that investigating that nonsense further is worth a few more hours of my life. Also, there is the Cabbage Soup Diet, which is based on the supposed negative calorie value of cabbage and other vegetables put in a soup. Or something like that.
Clever Rules for Negative Calorie Counting
Anahad O'Connor, author of the "Really" column in the New York Times, in his book Never Shower in a Thunderstorm: Surprising Facts and Misleading Myths About Our Health and The World we Live In 5, relates some funny stories of readers who wrote into the Times with some clever rules for "negative calorie counting." Most of these are obviously jokes, but the author does not really say so. Thing is, I've heard people say things like this so at least some of them may not have been joking. Here are the highlights:
- With foods like steamed crabs, it takes more energy to get at the crab meat than the crab actually contains. Therefore, you have to factor in the calories used in getting to the food in the first place. Marylanders rejoice!
- The cold beer rule: Cold beer has negative calories since it takes more energy to bring the beer down to body temperature than there is calories in the beer. Given the typical calorie count of beer, you'd have to say this one with a grin on your face and your finger crossed behind your back.
- The body can't count, so count your food, not your calories. This one says that your body cannot count very high so eat in multiples and make sure to eat so many of each thing that your body reaches its counting limit. Anything over this limit has no calories. Apparently, anything over six silver-dollar pancakes, your body cannot recognize. If the person who wrote in this one wasn't joking, they have serious mental deficiencies.
- Anything you resist eating…you get to subtract from your calories for the day. That's right..the temptations you don't give in to are negative calories. If you turn down a big chunk of chocolate cake, that's 400 calories less at the end of the day. Just today, I refused to eat cake, M&M's, and Doritos. I also avoided two Dr. Peppers which were taunting me. That puts me at, I don't know, 1500 calories down?5
Ice Water and Negative Calories
Ice water gets a lot of credit for its negative calorie effects. You saw the cold beer thing above right? Well, beer contains calories. How much better to drink ice water, with no calories. Why, it takes so much energy to warm that cold water up to body temperature, you could cancel out a whole meal by drinking ice water! Really? Of course not. But you could cancel out some of it though, right?
Let's see. For each gram of ice water the body will have to use about 37 calories to raise the temperature to body temp. Hey, this is looking good! I think we're on to something. Now, if I eat 3000 calories, I just need to figure out how much ice water I need to drink. It shouldn't matter when I drink it; I can drink it throughout the day or all at once, whatever. So, a gram of water is equivalent to a cubic centimeter of water:
(37 cal/cc)(#cc) = (3000 x 103 cal)
Okay, so I divide 37 into 3000, and I get 81 and then, that leaves me with #cc = 81 x 103 cc. So…the answer is 81 liters, or 20 gallons. It will take 20 GALLONS of ICE water to burn those calories. Oops.
Well, I only need to burn off that extra 500 calories.
(37 cal/cc)(#cc) = (500 x 103 cal).
That is so much better. You can do that with only 13.5 liters of ice water. That is about 3.5 gallons. You try it and let me know how it works out for you. By the way, chewing the ice cubes works even better. That takes 80 calories for each gram of ice. Nice! And cold.
I know you are impressed with my math. Sucker! I can't even help my son with his fourth grade math, half the time. I got help from Back-of-The-Envelope Physics by Clifford E. Swartz, which is the only kind of physics book I can understand, except the kind of physics in most science fiction books.6.
Chewing Your Way Thin
I mentioned calories burned by chewing above. A lot has been made, in books and articles, about a study published in the New England Journal of Medicine back in 2007 7, usually given as "a doctor from the Mayo Clinic," which found that chewing gum burns 11 calories per hour. Eh, so that's a lot of chewing, and I have TMJ problems, so I had to give up gum. But, it's not like there is nothing to this. You see, there are more things to consider besides just the calories burned by the chewing. Maybe you avoid a high calorie snack. Or maybe there is an appetite suppression, or it contributes to resting energy expenditure in some way. Tom Venuto blogged about this, and brought up another study that dove further, so you can find out more in Does Chewing Gum Help You Lose Weight?
Here's the thing: I don't know about you but I find people who constantly chew gum to be a bit repulsive. Sorry to any dedicated gum chewers reading this but, it's a little off-putting to have someone chewing their cud while talking to you. So, consider that if you try the chewing gum diet, you may not be able to sit with me at the cool kid's table.
The Protein Paradox and the Thermic Effect
Remember, above, I mentioned that the thermic effect of food is affected by the composition of a meal. So, protein and carbohydrates have a greater thermic effect than fat. This could be one reason for the association of fat with weight gain. But, traditionally, it was high-carbohydrate diets that got a lot of flack for weight gain. Therefore, many people began promoting a diet high in protein and low in carbohydrates. These diets would have 30% or greater energy from protein.
Problem is, a high-protein diet tends to be a high-fat diet. Diets high in saturated fat are not considered healthy, as you well know (a subject of debate). But also, fat makes you fat, right? Yet, these high-protein diets generally seemed to work. Well, now, most diets that limit calories "work." Okay? Let's get that straight. It's tends to be adherence that is the key, not the particular fad diet.
Of course, everyone does not believe that so there has to be some explanation for the observations of success with high-protein diets, despite the increase in fat intake. One of those explanations was that protein has a greater thermic effect than either carbohydrates or fat. So maybe all that protein intake contributed to thermogenesis to a significant enough degree. It does seem to be the case that meals higher in protein result in greater energy expenditure. However, estimates of the total energy increase after consuming a high protein diet (30%) as compared to "normal" protein diets, found only about a 23 calorie increase. That hardly amounts to a hill of beans for someone trying to lose weight. It is doubtful that high-protein diets exert their effect by increasing TEF.
Negative Calories and the Dieter's Paradox
The belief in negative calories is part of the kind of thinking involved in what Alexander Chernev calls The Dieter's Paradox. The kinds of foods promoted to be negative calorie foods fall into the category of healthy foods, for the most part. People are being encouraged to eat more healthy foods. In fact, it is outright shouted by every health organization in the world. Eat more healthy foods! Eat more fruits and vegetables; everybody needs to! This has been going on for a while. Yet, there seems to have been no impact on the obesity epidemic. According to Chernov, "An important factor contributing to this obesity trend is the misguided belief about the relationship between a meal's healthiness and its impact on weight gain, whereby people erroneously believe that eating healthy foods in addition to unhealthy ones can decrease a meal's calorie count."
Chernov asserts that although lack of willpower to control consumptive behaviors is often given as the chief cause of the still rising proportion of overweight people, this is not the only factor. He argues that over-consumption "might also stem from people's misguided belief about the relationship between a meal's healthiness and its impact on weight gain."
And there may be something to that. He gives the example of adding a side salad to an unhealthy meal and believing that the healthy option added to the unhealthy meal decreases the calorie count of the meal. This "halo effect" of healthy foods is believed to extend not only to the nutrient quality of the meal but also to its effect on weight gain. A side salad 'cancels out' other calories because of the negative calorie bias.8
Have you seen this behavior? Have you exhibited it? I've seen it. Two big macs and a side salad, anyone? This belief in protective effects is just one part of the dieter's paradox. The paradox, in general, is that the most weight-conscious people, especially dieters, are more prone to making irrational decisions about food, and therefore more prone to weight gain!
In chapter 4 of the book, Leveraging Consumer Psychology for Effective Health Communications, Chernov and co-author Pierre Chandon name this negative calorie bias is one of several biases that cause people to make errors in their estimation of caloric intake. The negative calorie bias falls under a larger bias, called the halo bias. Another main category of underestimation bias is the averaging bias.
Chernov says the halo bias "refers to the tendency of a particular feature of the food, such as nutrition labels or marketing claims that it is healthy, to influence the overall estimation of the calorie content of the food item or of an entire meal." And "the averaging bias refers to people’s tendency to average the calorie content of combinations of healthy and unhealthy items."
The problem with the idea of the halo bias is that the higher the actual calorie count of a food is, the more people tend to underestimate it. In a quick evaluation of a clients problem with his middle-age paunch, for instance, I asked him to list out his meals for a few days. He, of course, didn't think he was eating much and had no idea where all the calories were coming from. Typically, you will find that your clients have been severely underestimating (informally) the calories actually contained in the highest calorie items they tend to eat. For this client, the big problem was the habit of getting take-out lunches from convenience stores and consuming some "large-ticket" items without a clue as to the huge amount of calories he was taking in. Accordingly, he was eating a "healthy" turkey sandwich, for instance, but was chasing it with a large (jumbo) sweetened bottled iced tea that topped 500 calories, a large snack pack of potato chips or other chips that easily did the same. He simply severely underestimated just how many calories were coming from the most calorie laden things in his lunches. Comparably, his typical breakfast and dinner was healthy and moderate. It was easy for him to drop up to 1000 calories a day by just changing a few lunch habits! Hardly a life-changing feat. But this was not the "halo-bias" it was just a basic problem: the more calories a food actually contains, the more our estimates will fall short.
So, Wansink and Chandon controlled for this in a study where they asked consumers to estimate the number of calories in two ten-ounce cups. One contained M&M's and the other contained granola. Guess what? You may not have guessed this but both of these have pretty much the same number of calories. The M&M's contain 1,380 calories and the granola contained 1,330 calories. What do you think happened? Of course, the participants underestimated the calories in the granola, by 28% while overestimating the calories in the M&M's by 9 percent. This is consistent with the perception that granola is a "healthy snack" and that M&M's are not.
The halo bias is also caused by food label claims and other marketing descriptions. So claims of "low fat" or "healthy" will cause people to underestimate the true calorie count. These general effects are not isolated to the over-weight and calorie conscious but are also present in normal-weight people. So there is a lot more to it, of course, than one bias.
Even though a persons chief goal is to control caloric intake, the way they categorize different types of food as "healthy" or "unhealthy" will cause them to underestimate the calories in a meal, based on this perception. In reality, the number of calories in a meal is nothing more than the calories contained in each food item added together. But people often do not rely on reality to help them choose a meal, instead they rely on impressions. Consider the example given by Chernov and Chandon. You are limiting calorie intake and you have a choice between a hamburger or a hamburger and a side salad. You choose the hamburger and side salad. This is inconsistent with your goals, logically, because the two-item meal contains more calories. But you chose the higher calorie option.
What is going on here? For one, you may have perceived the salad as imparting some "benefits" to your health, such as vitamins, fiber, etc. The addition of a beneficial and healthful food, then, caused you to categorize the meal with the hamburger AND salad as more healthful than just the hamburger. The idea that something is more helpful can cause you to underestimate its calories..even with the 'math' in plain site. Biases, remember, are largely unconscious. You "averaged out" the low calorie and healthy salad with the high calorie hamburger causing you to derive a lower calorie estimate: This is the averaging bias. These biases are interrelated, as you can see.
Now, you might be thinking, the salad thing is just the negative calorie bias! That would make sense, at first glance. A person might believe that the greens in the salad consumed more energy to process than they gave, so that they actually ended up subtracting a bunch of calories from the meal. Well, some people might believe this but the negative calorie thing is more a fad belief than a consistent bias. In fact, when asked to consider such foods alone, consumers will not tend to assume they have zero calories or negative calories, but will give an actual calorie estimate.
To test this, Chernev and Gal asked participants to estimate the calorie content of a cheeseburger alone, a broccoli salad alone, or a meal containing both. The average calories given for the cheeseburger was 761 calories. The average calories given for the broccoli salad was 67 calories. Okay, so you can see that the participants did not perceive the broccoli salad as having negative calories, when viewed alone, despite broccoli frequently being viewed as negative calorie food. They gave a positive estimate. when we look at the combined meal group, the one who evaluated the cheeseburger and broccoli salad together, we should expect to get a number that is a combination of both the cheeseburger and broccoli salad number, approximately 830 calories, right? Wrong. This is not what happened. Instead, the combined meal group estimated that the cheeseburger-broccoli combo had 583 calories. That's 178 calorie LESS than the cheeseburger alone group. What seems to have happened is the averaging bias and the halo bias. The broccoli's perceived health benefits contrived to produce a lower estimate for the combined meal.
Just to be sure, they asked another group to compare a cheeseburger and a cookie in the same way. The cookie had the effect we would expect, causing the combined meal to be perceived as the highest calorie option.9 To read more about these studies and biases, see the references below.
Basal Energy Expenditure, BMR, and Resting Energy Expenditure: What's the Difference?
As I explained above, one of the three main components, and really the main component, of your daily energy expenditure is your resting energy expenditure. Yet, you may not have come across this term before, and instead have been exposed to the terms basal energy expenditure and/or basal metabolic rate. Many times these terms are used interchangeably. Most fat loss experts on the internet tend to prefer the term basal metabolic rate, or BMR, for short.
You may have seen formulas, such as the Harris-Benedict Formula (Equation) that are used to determine your BMR. Well, unless you fast a lot and never get out of bed, this is a bit incorrect, in more ways than one. The terms "resting" and "basal" do not quite mean the same thing, when used in these terms.
Both resting and basal energy expenditure are estimates of the energy needed in a 24 hour period.
Basal refers to the minimal level of metabolism needed to keep you alive. Resting refers to basal energy expenditure and is usually measured in a clinical setting, while lying at rest after a good sleep, after at least a 12 hour fast. Also, the environment is thermo-neutral so that the subject does not produce heat by shivering. The basal metabolic rate is measured and this is extrapolated to a 24 hour period. RMR is a a bit different and researchers usually measure this about 3 or 4 hours after a person eats or does significant physical activity. The RMR is measured and this is extrapolated to a 24 hour period. So, the RMR, and thus the REE, is slightly higher than the BMR and BEE. But, it's really not that significant.
As you probably guessed, the whole basal thing is a bit impractical, having to meet ideal conditions and all of that. It is okay to use these terms interchangeably but what we really want, technically speaking, are estimates of our resting energy expenditure, combined with our TEF and the energy used in physical activity.
This page created 10 May 2012 21:17
Last updated 23 Feb 2015 22:43