Caloric Deficit Versus Muscle Loss

[Greg Mihalik]

 

From a McMaster University Study –

For the study, 40 young men underwent a month of hard exercise while cutting dietary energy they would normally require by 40 per cent of what they would normally require.

The researchers divided their subjects into two groups. Both groups went on a low calorie diet, one with higher levels of protein than the other. The higher-protein group experienced muscle gains — about 2.5 pounds — despite consuming insufficient energy, while the lower protein group did not add muscle.

The lower-protein group at least had the consolation of not losing muscle, which is a predictable outcome of cutting calories and not working out, say researchers.

“Exercise, particularly lifting weights, provides a signal for muscle to be retained even when you’re in a big calorie deficit,” says Phillips.

 

Yes, n=40 is small, and I don’t know if 30 mile days with a 15 pound pack qualifies as “lifting weights”, but it could be enough of a “signal” to retain muscle.

Perhaps the lore about muscle loss due to hiking with a caloric deficit needs to be reconsidered.

[Anonymous]

I think it would depend on the makeup of the restricted calories.  If it contained adequate complete protein to replaced muscle cells damaged during a day of hiking, there should be little, if any, muscle loss, as long as the hiker’s body fat supplied enough calories to make up for the daily deficit.

When that body fat is exhausted, one of two things will happen.  Either the hiker will stop hiking, or his body will begin to use muscle protein as a source of energy to replace the calories previously supplied by body fat.  This is an unsustainable situation.

[Jeremy and Angela]

From the referenced paper:

Low Protein group (1.2g/kg/day):
15% protein, 50% carbohydrates, and 35% fat

High Protein group (2.4g/kg/day):
35% protein, 50% carbohydrates, and 15% fat

Both groups were overweight (~98kgs, BMI ~29, body fat ~24%).

-J

[Greg Mihalik]

Both groups were overweight (~98kgs, BMI ~29, body fat ~24%).

 

Excellent sleuthing! (I didn’t dig deep enough.)

And that explains soooo much.

[Hiking Malto]

here’s the news flash on this article.  It completely shatters what I believe is a myth that ” short term” hikers should carry a high fat foods.  What is a short term hike?  That will be different for everyone, but I would describe it as a hike of short enough duration that the body can rely of fats stores for a sufficient amount of energy.  That is clearly what is happening in this study, carbs stay constant, less fat, more protein with amble supply of fat for fuel.  The high calorie (fat) density myth has become almost an universal truth especially on this site and it is unfortunate.

[Anonymous]

“The high calorie (fat) density myth has become almost an universal truth especially on this site and it is unfortunate.”

A huge +1 to your entire post!

[Jerry Adams]

I don’t think that myth is debunked : )

The people were overweight and they did heavy, muscle building exercise.

Backpacking is not muscle building exercise.  If you gained no weight that would be fine.

If you’re overweight, you will have more body fat to consume.  Maybe replace some of it with muscle.

But the savings of substituting carbs or protein with fat is small.  Back of envelope – if you carry 1 pound of food per day, and replace 20% of it that’s carbs or protein with fat that has twice the caloric density, you’de save 10% of your weight or 1.6 ounces per day.  6 ounces for 4 days.  That’s something…

[Roger Caffin]

Both groups were overweight (~98kgs, BMI ~29, body fat ~24%).
And that explains soooo much.

Exactly. There’s no mystery here, except that the ‘researchers’ were silly enough to start with overweight people without realising what thet would mean.

I remember one guy went walking for a week on 400 g dry food per day. I was a bit surprised, as we normally reckon on 700 – 750 g dry wt per day. In discussion, he admitted he had lost about 400 g of body fat per day as well …

Cheers

 

[Hiking Malto]

How many hikers are on the trail doing short term hikes that don’t have sufficient fat reserves to provide energy for their hike.  Even low body fact individuals are carrying 10,000s of calories in fat.  Plenty enough to provide energy for a short duration hike.  So it is exactly what was tested in the study, individuals having sufficient energy in fat reserves.

[Anonymous]

“I remember one guy went walking for a week on 400 g dry food per day. I was a bit surprised, as we normally reckon on 700 – 750 g dry wt per day. In discussion, he admitted he had lost about 400 g of body fat per day as well …”

Exactly what would be expected.  The only remaining question in my mind would be did he have adequate dietary carbs to support fat catabolism, or did he end up using muscle protein?

“How many hikers are on the trail doing short term hikes that don’t have sufficient fat reserves to provide energy for their hike.  Even low body fact individuals are carrying 10,000s of calories in fat.  Plenty enough to provide energy for a short duration hike.  So it is exactly what was tested in the study, individuals having sufficient energy in fat reserves”

+1

 

Sorry, Jerry, myth debunked.. Both diets in the study had plenty of carbs to support fat catabolism.

 

[Roger Caffin]

The only remaining question in my mind would be did he have adequate dietary carbs to support fat catabolism, or did he end up using muscle protein?

If I remember correctly, he was running on salami, cheese and either oats or biscuits of some sort. I think he had to ration himself each day.

Cheers

 

[Hiking Malto]

“But the savings of substituting carbs or protein with fat is small. Back of envelope – if you carry 1 pound of food per day, and replace 20% of it that’s carbs or protein with fat that has twice the caloric density, you’de save 10% of your weight or 1.6 ounces per day. 6 ounces for 4 days.”

I wouldnt replace lace the fat with carbs, I would eliminate the fat and save the 12 oz.  Why carry extra fat, most people have plenty.

[Anonymous]

“If I remember correctly, he was running on salami, cheese and either oats or biscuits of some sort. I think he had to ration himself each day.”

There are carbs in all of those items, some more than others, so it would be a case of how much oats, biscuits, etc.  In any case there is also a lot of protein there, so it would seem at least plausible between the two that he had enough dietary sources to at least partially spare muscle protein..

 

[Terry Sparks]

From my own experience thru-hiking the PCT in 2014 and, looking at my fellow hikers along the trail, it became obvious by the time I got to Oregon my body was first using it’s reserves from the area’s not engaged in continuous exercise, such as the chest, arms and torso. While watching these parts of my body shrink in size from loss of body fat and then muscle, my lower body, legs and glues, continued to strengthen  grow in size.  My body was taking stores from where it wasn’t needed to fuel the muscle being used.

[Bill Segraves]

“here’s the news flash on this article. It completely shatters what I believe is a myth that ” short term” hikers should carry a high fat foods. What is a short term hike? That will be different for everyone, but I would describe it as a hike of short enough duration that the body can rely of fats stores for a sufficient amount of energy. That is clearly what is happening in this study, carbs stay constant, less fat, more protein with amble supply of fat for fuel. The high calorie (fat) density myth has become almost an universal truth especially on this site and it is unfortunate.”

I’m not sure I follow this. Mightn’t it be the case that high fat and high protein, with reduced carbohydrate, would do just as well? (And at a lower weight of total food carried.)

Cheers,

Bill S.

[Bill Segraves]

“From my own experience thru-hiking the PCT in 2014 and, looking at my fellow hikers along the trail, it became obvious by the time I got to Oregon my body was first using it’s reserves from the area’s not engaged in continuous exercise, such as the chest, arms and torso. While watching these parts of my body shrink in size from loss of body fat and then muscle, my lower body, legs and glues, continued to strengthen grow in size. My body was taking stores from where it wasn’t needed to fuel the muscle being used.”

I’ve observed this, too. Haven’t seen a good study on it, but there are studies describing plausible mechanisms for how this would work. Depending on one’s priorities, it might be appropriate to think of those muscles not used for backpacking as “protein stores”! ;)

Cheers,

Bill S.

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