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Welcome all seeking refuge from low carb dogma!

“To kill an error is as good a service as, and sometimes even better than, the establishing of a new truth or fact”
~ Charles Darwin (it's evolutionary baybeee!)

Saturday, March 12, 2011

Does exercise make you hungry?

Thanks to MM, I now have the full text of the following study.  I'm going to do a test for sharing this with y'all through Google Docs.  Please let me know if it doesn't work:


Acute compensatory eating following exercise is associated with implicit hedonic wanting for food  (I'm going to intersperse quotations from all over this paper)

The efficacy of exercise to promote weight loss could potentially be undermined by its influence on explicit or implicit processes of liking and wanting for food which in turn alter food preference. The present study was designed to examine hedonic and homeostatic mechanisms involved in the acute effects of exercise on food intake.
Physical activity is currently strongly promoted as a method of weight control. However, in some individuals, a compensatory increase in energy intake (EI) might serve as a barrier for the potential for exercise to promote a negative energy balance [1].  Therefore, the efficacy of exercise as a successful method of weight management will vary between individuals [2]. EI is commonly put forward as the compensatory mechanism responsible for a lack of, or lower than expected, exercise-induced weight loss. 
Bottom Line:  Like most things, there's a high degree of individual variability and this depends on more than just physiological homeostatic signalling. 
24 healthy female subjects were recruited to take part in two counterbalanced activity sessions; 50 min of high intensity (70% max heart rate) exercise (Ex) or no exercise (NEx). Subjective appetite sensations, explicit and implicit hedonic processes, food preference and energy intake (EI) were measured immediately before and after each activity session and an ad libitum test meal.
The protocol is shown below:


Two groups of subjects were identified in which exercise exerted different effects on compensatory EI and food preference. After exercise, compensators (C) increased their EI, rated the food to be more palatable, and demonstrated increased implicit wanting. Compensators also showed a preference for high-fat sweet food compared with noncompensators (NC), independent of the exercise intervention.
Sweet fats seem to be an achilles heel for lots of people.  Think ice cream!  Another way to look at this is perhaps those who prefer this sort of food tend to compensate in some sort of "reward" means.
Exercise-induced changes in the hedonic response to food could be an important consideration in the efficacy of using exercise as a means to lose weight. An enhanced implicit wanting for food after exercise may help to explain why some people overcompensate during acute eating episodes. Some individuals could be resistant to the beneficial effects of exercise due to a predisposition to compensate for exercise-induced energy expenditure as a result of implicit changes in food preferences.

So how many are we talking about?  Well here's the graphic for all the participants and caloric compensation:


Note that the ad libitum test meal "consisted of cheese salad sandwiches, ready-salted crisps and fruit yoghurt. The average percentage energy provided by protein, fat and carbohydrate in the test meal was 13%, 45% and 42% respectively."

The groups all expended ~150 cals in their exercise bout.  The zero line indicates no change in intake and the dashed line is the "break even" point for increased intake to negate energy expended.  Out of 22 participants, I think it's fair to say that 8 or 9 essentially made no compensation at all.  Thus about 40% of folks have no effect of exercise on intake and would lose weight by exercise alone.   The authors used the 0 line to delineate 11 compensators from 11 non-conpensators but the intake difference of at least two C's is negligible.  I think this is a bit deceiving when one sees how close 2 compensators are to that zero line.  A 13/9 split seems more reasonable to me.

Another 2 compensated only to negate the increased expenditure, and 2 more increases intake by only around 100 cal and another 2 by about 150 cal - not a lot of high fat sweets needed!   These 6 would probably benefit from exercise for weight loss with just a little attention to intake.  Don't eat ad libitum from relatively high energy density foods (high fat and carbs all).  Perhaps eat some veggies or real fruit and leave the crap alone.

Then there's the 5 who overcompensated to varying more significant degrees +200 to +500 from break even and net +350 to +650 cals.   Again, if they're eating ad libitum from crap like that offered, this is no surprise.  Have a normal low carb or low fat or whatever your weight managing real foods meal, and perhaps exercise a little portion control.

But we also see that even with that crap test "meal", 3 of 22 significantly decreased intake.  Now it is fair to point out that more participants overcompensated than undercompensated, but given the food choices, all this study ultimately demonstrated was that roughly one quarter of the women will overeat SAD foods following exercise.  A full 50% were no hungrier for SAD crap after exercise than before, and some were significantly less hungry.

Thus Gary Taubes' assertion that all exercise does is make you hungrier and essentially that this is all a homeostatic reaction is wrong.  

21 comments:

John said...

I will start off by disagreeing with your final assertion. If people do not lose weight by exercising, then one of two things must be happening: 1. they are eating more to compensate, or 2. their internal homeostatic mechanisms are decreasing their metabolic rate. I would technically classify both of these as homeostatic mechanisms.

I am working my way back through your blog posts, so if there's a good study showing that exercise does in fact provide significant weight loss, I apologize. Most of the studies I've seen show no statistically significant effect of exercise on body weight over long time periods.

And no, this study does not even show that Gary Taubes' assertion is wrong. They only followed the participants for the meal immediately following exercise. That is not sufficient. You would need to perform exercise on multiple days, with all meals recorded to ensure that there isn't compensation at other times (and check for variation in individuals feeding post-exercise). I wouldn't be surprised to see some folks dislike eating right after exercising, but gorge themselves later.

I absolutely agree with your position that the low-carb community needs a bit more sanity about this stuff, but I hope you don't pull things too far the other direction just to be contrary to Gary Taubes. Considering the amount he's written on the topic, he's likely to be accidentally correct at least a few times. ;)

Alan said...

Many people over-eat after exercise for hedonic reasons alone. That has nothing to do with metabolic homeostasis. That is "the idiot behind the wheel".

If ther is ignorance of how few calories get burned by.... it's from not wanting to know. The information is WIDELY available!

CarbSane said...

Hi Alan, so nice of you to stop by my lonely blog and grace us with your wisdom and presence!

CarbSane said...

@John: Welcome! I would suggest you read this other post of mine on this topic:
http://carbsanity.blogspot.com/2011/03/exercise-weight-management.html

Those who compensate by upping intake may be doing this for reasons OTHER than genuine hunger. I ran around all day as a kid and I don't recall being hungry all the time. I've never lost weight because my hunger was abated by becoming a couch potato.

There is no evidence for a dialing down of metabolic rate in response to exercise. There's evidence that exercise can help maintain metabolic rate in dieters and maintain lean body mass.

Taubes speaks in absolutes: Exercise is useless for weight loss because it makes us hungry and eat more, and it makes us lazier the rest of the day. Controlled studies show otherwise for many, most or all depending on the study and effect being looked at.

A broken clock is right twice a day. ;-) I guess everything I write wouldn't be so counter to Taubes if his references and the vast bulk of scientific research didn't contradict his assertions at every turn.

Flavia said...

This is my n=1, but exercise does not make me hungry, at least not in the short term. I think it is because of-
1) Exercise takes up time when I could be eating/thinking about food
2) Lots of jerky or up/down movements tend to give me mild stomach upset which results in lack of hunger
3) I don't want to "waste" my exercising by eating poorly
4) Adrenaline rush decreases hunger

When I used to exercise more (and more often) sometimes I would wake up ravenous, but I think by then I had given myself a very big caloric deficit and needed to at least partly make up for it.
Gosh, I really need to get back to the gym. But I hate the gym. Do you exercise at home? Any suggestions? Maybe I'll do some HIIT during commercials...hmmmm

Stephan said...

Hi Carbsane,

I think it's difficult to draw much of a conclusion from a one-day study like this. Long-term homeostasis responds to changes in fat mass, which would be insignificant after one bout of exercise. The fact that exercise alone isn't a very effective fat loss tool does imply some level of long-term homeostasis. That being said, there is variability and some people can successfully lose fat by exercising. Others will gain fat, like my friend who went from lean to having a pot belly during his marathon training. It subsequently disappeared after he stopped training. But that isn't typical.

My current thinking is that it's good to have something on the expenditure side of the energy balance equation, because that's how our bodies are designed to operate. Exercise probably works better as a preventive measure against fat loss, perhaps because it keeps the homeostasis mechanisms running smoothly.

James Krieger said...

Stephan,

If you look at the long-term RCT's, they indicate that exercise doesn't help much with weight loss, but it does help tremendously with weight maintenance after that loss. This is also supported by observational data from the NWCR, where much of this population engages in large amounts of physical activity. Both the observational and experimental data point to a weekly threshold of approximately 2500 kcal/week of activity as important for long term maintenance.

Todd Hargrove said...

James,

Do you have a theory to explain why exercise works better to keep weight off than to lose it?

James Krieger said...

Todd,

Research shows that weight loss results in a decrease in energy expenditure that is greater than you would predict based on the weight loss alone. This is true even if the weight loss has been maintained for over a year. I have a series of articles on this on my site, starting with thise one:

http://weightology.net/weightologyweekly/?page_id=415

It is likely that exercise helps counteract this phenomena. This is important particularly because people's caloric intakes are likely to start to creep back upwards over time.

CarbSane said...

@Flavia: I concur with 1,3 & 4 for me. I hate gyms for exercise as I don't really like to exercise in public. I much prefer my DVD's. But I've just found a reasonable club in my area with racquetball!! I may join because I'm definitely looking into something more *sports* than exercise. I do spontaneous little bouts of activity these days. I've described several times how I do the Flashdance maniac footwork while I'm cooking. And I make a good workout out of getting firewood from our pile. I run up and down the stairs in my house ... things like that. I know that, for me, regular exercise will be required to lose some more weight.

CarbSane said...

@Stephan: This post was prompted by a discussion I was having over on Taubes' forum. It was offered up as proof that "all exercise does is make us hungry" canard. This study certainly is not proof of that, but SOME people will overcompensate. Thus his absolutist statement is wrong.

As an anecdote, I was an extremely active kid and I don't recall going around hungry all the time. Same in high school when I played organized sports year round and had active jobs in the summers as a sports counselor and lifeguard. During my roller-coastering weight days I was leanest during two periods. One when I did Nautilis and played racquetball a LOT and the other when I trained and did a sprint triathlon. That latter period being the time I described in my interview with Jimmy when I didn't count calories but I certainly ate less. Neither of those periods did I lose weight and spontaneously decide to exercise, rather I exercised and lost weight.

Don't know what to make of your marathon friend other than it is possible weight was redistributed to visceral depots for more ready access? I tend to carry weight in my upper arms and thighs and was just discussing with a friend of mine that running, and no other activity, seems to cause me to lose fat from those areas. Maybe I just didn't put it in my belly as my former body type almost never did that.

CarbSane said...

To everyone: James stresses an important issue regarding exercise and that is it's utility in preventing regain. I would add to that not gaining the weight in the first place.

In this previous post for weight loss two of the studies cited showed increased TDEE for the exercisers. In the study on obese women, the exercisers lost more fat mass despite consuming more calories to compensate for the calories burned during the exercise itself. We know calorie restriction will tank our metabolisms, and that's what makes the "LC is not calorie reduced" myth so misguided.

Weight loss is useless without maintenance. If one exercises during weight loss, there is retention of total energy expenditure. The FO can eat a bit more than their non-exercising counterparts. I gotta say, even 700 cal/week difference in this can go a long way towards making life more "liveable".

Flavia said...

Well, I am going to start exercising (more than my twice a week walks) to see if I can finally drop these last 5-10 pounds. I'll let you know if exercise has any effect.

Rob said...

I think what's best, both in energy expenditure and less stress on the body, is just being more active via NEAT. If you have a job that keeps you on your feet say 8 hours a day, that's a huge amount of calories burned.

But at the end the day the saying "you can out run a bad diet (meaning hypercaloric!)" is very accurate.

And for another anecdote, I do fasted resistance training 3-4 times a week and it kills my hunger. Maybe this is just specific to weight training but I could easily not eat for 1-2 hours after a short but intense training session.

Sanjeev said...
This comment has been removed by the author.
Sanjeev said...

Rob said...
"you can out run a bad diet (meaning hypercaloric!)" is very accurate.
______________________
It's very unfortunate that it's true.

The very first time I was skinny was when I was doing a metric ton of cycling every day.

for more than a year my diet stayed about the same and I dropped a lot of weight. Around 2 years into that people started complaining that I looked really unhealthy and I wanted to ride much more. I consciously started eating a lot more. My diet got immeasurably worse around this time - eventually I had added several litres of ice cream per week and several chocolate bars per day.

A couple of months of non-cycling (forced by an accident) and I had more fat mass than ever before.

In my more recent experiences with cycling and judo I noted very carefully when I increased my calories and I made sure that when I stopped doing hard labour or play for an extended period that I reduced my calories substantially.

CarbSane said...

Welcome Rob! I did formal intermittent fasting (Fast 5) for 3 months solid in Summer 09 and was often hungry in those last hours before breaking the fast. Thus that's when I would go for my walk or bike ride. I often came back and had to "force" myself to eat in order to get enough calories into my body. Twas a misguided strategy in retrospect. I should not have worried over getting "enough" calories, but that's irrelevant. And those days when I didn't eat much, I wasn't ravenous later or more hungry the next morning or anything of the sort.

Yeah Sanjeev, this is why former athletes tend to gain weight ... Duh! And why so many of my male friends gained weight in their 40's. Men tend to (on average) be "lucky" for longer in terms of their eating. Then their metabolisms slow a bit and they aren't veterans of carefully watching what they eat so ... bingo!

Razwell said...

* Infant obesity is increasing worldwide.

* Every single nation has an increasing obesity rate even poor African nations and remote islands.

We do not know how to take an obese person and make him lean, long term. This is the fact.

Exercise is next to useless as an obesity treatment. It's not a panacea at all.


It is more than time for the medical establishment to take responsibility for the complete failure of their method, and STOP blaming patients. ( "eat less, move more" nonsense nostrum)



The caloric hypothesis is DEAD. Time to move on.

And even top tier obesity researcher Dr. Friedman admits as much.

Nigel Kinbrum said...

Oh Razwell,

ELMM works. You just have to know how to make it work. :-D

Nige.

Sanjeev said...

Manuel Uribe is still dead ... or is he?

How about Sam Clemens ? And Generalissimo Francisco Franco?

O Primitivo said...

Cross talk between physical activity and appetite control: does physical activity stimulate appetite? http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=816556

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