Friday, January 29, 2010

your most recent workout is the most important....and stay low carb

Now this one is interesting.... lots of implications

The abstract is below but some comment first (informed from this and this)

the study found that exercise enhanced insulin sensitivity, particularly when meals eaten after the exercise session contained relatively low carbohydrate content. Enhanced insulin sensitivity means that it is easier for the body to take up sugar from the blood stream into tissues like muscles, where it can be stored or used as fuel. Impaired insulin sensitivity (i.e., "insulin resistance") is a hallmark of Type II diabetes, as well as being a major risk factor for other chronic diseases, such as heart disease.

Interestingly, when the research subjects in this study ate relatively low-calorie meals after exercise, this did not improve insulin sensitivity any more than when they ate enough calories to match what they expended during exercise. This suggests that you don't have to starve yourself after exercise to still reap some of the important health benefits.

Insulin Sensitivity is of course a "good thing" - it means you need less of it for it to have an effect. An excellent primer on insulin matters is here.

What I found interesting were these comments:

This study follows up on several previous studies that demonstrate that many health benefits of exercise are transient: one exercise session produces benefits to the body that taper off, generally within hours or a few days.

"Many of the improvements in metabolic health associated with exercise stem largely from the most recent session of exercise, rather than from an increase in 'fitness' per se," Dr. Horowitz said.

What do we make of this?

  • The importance of consistency - regular training, might not make you "fitter" but each session is important.
  • Every workout is important - we tend to think of junk sessions, but every one matters
  • Exercise and nutrition go together - what you eat limits the effects of how you train.
  • It is still all about hormones
  • what type of workouts have the best effects - endurance, resistance, HIIT?

Energy deficit after exercise augments lipid mobilization but does not contribute to the exercise-induced increase in insulin sensitivity.

The content of meals consumed after exercise can impact metabolic responses for hours and even days after the exercise session. The purpose of this study was to compare the effect of low dietary carbohydrate (CHO) vs. low energy intake in meals after exercise on insulin sensitivity and lipid metabolism the next day. Nine healthy men participated in 4 randomized trials. During the control trial (CON) subjects remained sedentary. During the other 3 trials, subjects exercised (65%VO2peak; cycle ergometer and treadmill exercise) until they expended ~800 kcal. Dietary intake during CON and one exercise trial (BAL) was designed to provide sufficient energy and carbohydrate to maintain nutrient balance. In contrast, the diets after the other 2 exercise trials were low in either CHO (LOW-CHO) or energy (LOW-EN). The morning after exercise we obtained a muscle biopsy, assessed insulin sensitivity (Si; IVGTT) and measured lipid kinetics (isotope tracers). Although subjects were in energy balance during both LOW-CHO and CON, the lower muscle glycogen concentration during LOW-CHO vs. CON (402+/-29 vs. 540+/-33 mmol/kg dw, P<0.01) coincided with a significant increase in Si (5.2+/-0.7 vs. 3.8+/-0.7 (mU/L)(-1)(.)min(-1); P<0.05). Conversely, despite ingesting several hundred fewer kcals after exercise during LOW-EN compared with BAL, this energy deficit did not affect Si the next day (4.9+/-0.9, and 5.0+/-0.8 (mU/L)(-1)(.)min(-1)). Maintaining an energy deficit after exercise had the most potent effect on lipid metabolism, as measured by a higher plasma triacylglycerol concentration, and increased plasma fatty acid mobilization and oxidation compared with when in nutrient balance. Carbohydrate deficit after exercise, but not energy deficit, contributed to the insulin sensitizing effects of acute aerobic exercise. Whereas maintaining an energy deficit after exercise augmented lipid mobilization.


Marc said...

So what IS best to eat after exercise? (if not going for lipid mobilization)


Chris said...

I'd say what you eat is fine Marc!

Chainey said...

I followed that link to the Rosedale article, which was a bit of a nostalgia buzz as it was one of the first things, if not the first thing, I ever read about low-carb. Probably two years ago now.

Chris said...

I read that years ago too. I remember printing it out and reading it over and over. It really explains this well.

Anonymous said...

So, on a Low Carb diet, eating your carb's post workout is what is stated here?

Anonymous said...

no. I read it that carbs blunt the insulin sensitising effects of the workout

Anonymous said...

Perhaps the transient insulin sensitivity that occurs after exercise is similar to the "physiologic" (as opposed to "pathologic") insulin resistance that occurs with low carb, as explained by Peter. It's a temporary adjustment with no long term consequences.

Kipper said...

But "low carbohydrate" in the context of this study was 200g in a single meal!

meredith said...

I was listening to some old podcasts of one of those popular diet and fitness guys and he insists that immediately after intense exercise the body is temporarily insulin resistant due to lactic acid build up. He says that the ideal time to eat would be 30 to 60 minutes post exercise, once the lactic acid dissipates. Ever hear of this?

Anonymous said...

I find a subtle but very important difference between exercising to build up fitness of subsequent sessions and exercising because THAT session will provide direct benefits. This is far more motivating to make someone get out there I think.

Jim Purdy said...

I'm dealing with some health issues that temporarily limit my exercising, but I'm hoping my low-carb diet will be helpful until I resume exercising.

Interesting post and references. Thanks.

The 50 Best Health Blogs

Chris said...


actually that - rather than the low carb thing - was what I found most interesting. The idea that each workout is important in and of itself.