Is post-workout insulin spike necessary?

[Neal Winkler]

Excerpted from the first issue of Alan Aragon's Research Review:

Is It Necessary to “Spike” Insulin Post-workout?

Another concern of the fat-free-post-workout camp is the blunting of the insulin response. The rationale of maximizing the insulin response is to counteract the catabolic nature of the post-trained state, switching the hormonal milieu into an anabolic one, thus speeding recovery. Although this might benefit those who train fasted or semi-fasted, many don’t realize that a pre-exercise meal (and in some cases the mid-exercise meal) is doing more than enough spiking of insulin levels for anticatabolic purposes.

It’s an important objective to not only maximize muscle protein synthesis, but also minimize protein breakdown. However, the latter doesn’t require a massive insulin spike, but rather just a touch beyond basal/resting levels. To illustrate this, Rennie & colleagues found that even during a sustained high blood level of amino acids, no further inhibition of muscle protein breakdown occurred beyond insulin elevation to approximately 15 μU/l,20 which is slightly above normal basal levels of 5-10 μU/l.

To reiterate, the pre-exercise meal can have profound effects on insulin levels that surpass the length of the training bout. Tipton’s team found that as little as 6g essential amino acids + 35g sucrose taken immediately before exercise (45-50 minutes of resistance training) was enough to keep insulin elevated to roughly 4x above fasting levels 1-hour post-exercise.21 It took 2 hours post-exercise for insulin to return to resting levels. A similar insulin response was seen with 20g whey by itself taken immediately preworkout.22 If carbs were added to the pre-training protein, there would be yet a greater insulin response.

As far as solid food goes, Capaldo’s team examined various metabolic effects during a five hour period after ingesting a meal composed of 75g carb (47%), 37g prot (26%), and 17g fat (27%).23 Although this study didn’t examine training effects, this meal would make a nice post-workout meal due to its absolute (and proportional) amounts of protein and carbohydrate. The fat-fearing camp would warn against the meal’s fat content interfering with the insulin response. However, this meal was able to raise insulin 3 times above fasting levels within 30 minutes of consumption. At the 60 minute mark, insulin was 5 times greater than fasting. At the 300 minute mark, insulin levels were still double the fasting level.

Elliot and colleagues compared the effect of fat-free milk, whole milk, and a higher dose of fat-free milk (to match the calories of the whole milk) taken 60 minutes post-resistance exercise.24 Whole milk was superior for increasing net protein balance. Interestingly, the calorie-matched dose of fat free milk containing 14.5g protein, versus 8.0g in the whole milk (an 81% advantage), but still got beaten. The investigators speculated over the possible mechanisms behind the outcome (insulin response, blood flow, subject response differences, fat content improving nitrogen retention), but end up dismissing each one in favor of concluding that further research is necessary to see if extra fat calories ingested with an amino acid source will increase muscle protein synthesis. Lingering questions notwithstanding, post-workout milkfat was the factor that clinched the victory – at least in overnight-fasted subjects.

To put another nail in the coffin of the insulin spiking objective, post-exercise glycogen resynthesis is biphasic.25 Unlike the subsequent “slow” phase which can last several hours, the initial “rapid” phase of glycogenesis lasting 30-60 minutes immediately post-exercise is not dependent upon insulin. Maximizing post-workout hyperinsulinemia may be beneficial for athletes with more than a single exhaustive endurance-containing training bout separated by less than approximately 8 hours, but in all other cases, the benefit in “spiking” insulin is nil.

In line with this theme, interesting research has surfaced in recent years challenging the idea that highly glycemic (and thus insulinemic) carbohydrates taken post-workout are the optimal for recovery. Erith’s team found no difference between post-exercise high- and low-glycemic index (GI) carbohydrate intake on exercise performance the following day.26 In a similar study, Stevenson’s team actually saw better next-day performance in subjects who consumed low-GI post-exercise carbohydrate than those who consumed high-GI post-exercise carbohydrate.27

Is spiking insulin necessary post-workout? Generally not.

-No greater inhibition of muscle protein breakdown has been seen beyond insulin elevation to approximately 15 μU/l, which is slightly above resting/basal levels of 5-10 μU/l.

-In one study, whole milk was superior for increasing net protein balance post-workout, despite the calorie-matched dose of fat free milk containing 81% more protein.

-The initial 30-60 minute “rapid” phase of glycogenesis immediately post-exercise is not dependent upon insulin.

-There’s no need to attempt to spike insulin for recovery purposes since maximal effects are seen at minimal elevations. Simply getting enough total substrate surrounding the training bout suffices, at least within the context of a 24-hour separation between exhaustive training of the same muscles. Multiple depleting endurance-type bouts per day (i.e., < 8 hours between bouts) may be the exception to this rule.

-On a related tangent, it’s been commonly recommended to maximize post-exercise hyperglycemia and hyperinsulinemia by consuming high-GI carbohydrates. However, this strategy has been seen to offer no benefit on next-day performance, and one recent study even saw endurance impairment.

[Garrett Smith]

Nice post.

[Steven Low]

Well, I do know that insulin spiking does blunt GH response after exercise. So.. that's another negative for insulin spiking if that's the case.

T'was a good post. Is there any research that offers an antagonistic viewpoint to this?

[John Alston]

Originally Posted by Steven Low

Well, I do know that insulin spiking does blunt GH response after exercise. So.. that's another negative for insulin spiking if that's the case.

T'was a good post. Is there any research that offers an antagonistic viewpoint to this?

I've heard the DeVany doctrine of the pwo insulin blunting the GH release debunked or at least disputed by some study... I forget where. I think it was linked to by Shaf on another site, but good luck searching among his myriad of posts.
Anyway, if you're trying to gain, might be worth looking at the pwo chug as just a calorie opportunity, assuming you don't have too many issues with body fat.

[Mike ODonnell]

Eating alot of protein will also give an insulin response....so a big protein meal pwo also seems to be the natural response for the body. I doubt GH suffers much...as GH spikes in little peaks all day...but the big dose is at night. I personally just get fat and bloated on pwo shakes....so whole foods seems like a naturally better choice.

[Ari Kestler]

So if we IF and eat 2 large meals a day (with anywhere from 3/4-1lb of meat in them) are we shooting ourselves in the foot? I only ask because I tend to IF 1-7pm, and my workout is in there, so I normally only eat 2 large meals, rather than 4 small meals or something...is this unwise from an insulin standpoint?

[Mike ODonnell]

Originally Posted by Ari Kestler

So if we IF and eat 2 large meals a day (with anywhere from 3/4-1lb of meat in them) are we shooting ourselves in the foot? I only ask because I tend to IF 1-7pm, and my workout is in there, so I normally only eat 2 large meals, rather than 4 small meals or something...is this unwise from an insulin standpoint?

Are you gaining muscle and seeing results? If the answer is Yes, then don't sweat it. You have plenty of "quiet time" from insulin during IF. Using it in small doses is not going to be the end of the world. I would still say eat smaller meals before the workout and make the pwo the larger meal. But...many ways to play with all the numbers. Insulin is needed to shuttle the aminos into the muscle cells (hence why your body responds with insulin with large protein...sensing you made the "kill" and is now time to feast, relax and repair the muscles)...but your muscle cells need less insulin than fat cells...so little doses are fine. Sugar drinks pwo is not needed.

[Liam Dougherty Springer]

So is it the case that these studies are showing no benneffit to an increased carb to protien ratio PWO for recovery. Or just that it is not neccessary to use high GI carbs inorder to receive the desired results.

For instance currently I will consume a PWO meal of 8 carb blocks 4 Protein and 0 fat. I then balance my blocks by adjusting other meals in the day.

Should I just balance all my meals avoid hormonal spikes and receive the same results.

[Mike ODonnell]

Originally Posted by Liam Dougherty Springer

So is it the case that these studies are showing no benneffit to an increased carb to protien ratio PWO for recovery. Or just that it is not neccessary to use high GI carbs inorder to receive the desired results.

Just saying the thought of needing a "sugar" shake to spike insulin is not needed or even neccessary. I think "carb" timing to get in a majority of daily carbs (whole food) when muscle insulin sensitivity it at it's highest may do well for some esp with higher training loads and wanting to lose fat/gain muscle. But those carbs dont need to be loaded with sugar and you benefit more from whole food sources.

[Liam Dougherty Springer]

Originally Posted by Mike ODonnell

Just saying the thought of needing a "sugar" shake to spike insulin is not needed or even neccessary. I think "carb" timing to get in a majority of daily carbs (whole food) when muscle insulin sensitivity it at it's highest may do well for some esp with higher training loads and wanting to lose fat/gain muscle. But those carbs dont need to be loaded with sugar and you benefit more from whole food sources.

Okay that is reasureing information would it be a good Idea to stick to mostly VLCD veggies or would it be better to use some higher density veggies like colored vegetables roots and the borderline unacceptable sweet potatoes? Right now I enjoy useing coconut water, berries and an apple but I wonder if the large amount of fructose while lowering the Insuline response might alo give me less of the recovery benifits I am looking for. Or is the insuline response to these foods in your opinion even higher than would be desireable? Would adding fatsources such as nuts and Coconut shavings aid in slowing the GI while still allowing for sufficiant recovery in that PWO window of preffered glycogen restoration?