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From Fellrnr.com, Running tips
HMB
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* There's some evidence from animal studies that HMB may reduce insulin resistance<ref name="SharawyEl-Awady2016"/><ref name="FuBruckbauer2015"/>, though in high doses (equivalent of >50g/day in humans) one study found increased insulin resistance<ref name="YonamineTeixeira2014"/>.
* HMB doesn't raise insulin levels<ref name="WilkinsonHossain2013"/>, unlike protein, so it doesn't inhibit fat loss (lipolysis.) This is critical given it's use to improve fat loss.
* HMB is surprisingly cheap; buying in bulk from amazon.com (see below) costs less than $0.10 per dose (1 gram.)
=How I take HMB =
This isn't medical advice, just my approach that you can use as a starting point. I'm continually tweaking my training and nutrition, so by the time I've finished writing this it's likely to be slightly different! My approach assumes I'm trying to reduce my body fat while keeping or increasing lean mass, which is fairly normal for me. The calcium form of HMB (the cheapest and most widely tested) peaks in the blood about 30 minutes after consumption<ref name="WilkinsonHossain2013"/>, and has a half-life of about 2.5hours<ref name="FullerSharp2010"/>. This means that timing seems to be pretty important.
* I usually take ~1g of HMB in a dose, either mixed in a calorie free electrolyte drink or in a protein smoothie. The taste is a little musty but not unpleasant to me. I've had no GI issues with HMB, nor heard of any being reported.
* On rest days, I'll take HMB while fasting, often with some Vitamin C. I aim to take HMB about every 3-5 hour to push my body towards burning body fat rather than muscle. While I'd like to think the HMB will actually build muscle, I suspect that being fasted and calorie restricted makes this unlikely at this point in my day.
* I break my fast on rest days with Casein protein with HMB and Vitamin C. The idea here is to provide protein without raising insulin too much. I'm hopeful that I can extend the fat burning into this early part of the post-fast. (See "Casein has a lower insulin response than whey<ref name=or Whey?"ReitelsederAgergaard2011"/>below. That study showed casein resulted in a lower insulin response from 15 to 60 minutes, a peak insulin of ~110 v 180 for whey (pmol/L), and with a total insulin response (area under the curve) of 15.6 v 18.5 for whey.
* On rest days I will often do a brief [[High Intensity Interval Training]] session on the bike trainer. This is typically 4-6x 12 seconds at 7-9 watts/Kg with 2-minute recoveries. I mostly time the session around the HMB intake.
* On training days, I often will take HMB, with ~5g of Arginine, ~5g of Citrulline-Malate, and 6-8oz beetroot juice just before starting running. The goal of the other ingredients is to boost blood supply to the muscles.
=HMB Forms=
HMB is available as a calcium salt or as a free acid, with the free acid resulting in a more rapid rise in blood HMB levels, has nearly twice the area under the curve, and has 25% greater utilization<ref name="FullerSharp2010"/>. The free acid has a half life of ~3 hours and the calcium salt is ~2.5 hours<ref name="FullerSharp2010"/>. However, most research has been on the calcium salt, and the free acid form is more expensive, so personally I've only used the calcium salt.
=HMB Safety=
Since it's first use as a nutritional supplement in 1997, HMB has been extensively studied, and found to be safe in both human and rodents<ref name="WilsonFitschen2013"/>. There was one study that found high doses of HMB, the equivalent of over 50g/day in humans, increased insulin resistance<ref name="YonamineTeixeira2014"/>, though other studies show improved insulin resistance at typical levels (see above). However, contamination of supplements is an issue, with at least one athlete testing positive due to taking an HMB supplement<ref name="wada"/>.
=Casein or Whey?=
On a related topic, should you use whey or casein protein? (I'll ignore other types of protein for now.) I'd like to think that using Casein can extend the fat burning into this early part of the post-fast, but I'm not sure the research supports my optimism. Certainly, casein has a lower insulin response than whey<ref name="ReitelsederAgergaard2011"/>. That study compared 0.3 g/kg lean body mass of whey or casein in healthy subjects (that's just ~17g.) The casein resulted in a lower insulin response from 15 to 60 minutes, with a peak insulin of ~110 (casein) v 180 (whey), both pmol/L. The total insulin response (area under the curve) was 15.6 for casein v 18.5 for whey. It's not clear that the difference would change the impact on fat burning (lipolysis.) It only required 12 pmol/L of insulin to suppress 50% of lipolysis, 22 pmol/L to suppress 70%, and 34 pmol/L to suppress 90%<ref name="JensenCaruso1989"/>. This suggests that the difference between casein and whey isn't going to impact lipolysis.
[[File:Insulin Casein Whey.jpg|center|thumb|400px|]]
=Support This Site=
This is the HMB powder I use; it's the calcium form, which is much cheaper and more widely studied than the free acid.
{{Template:BuyAmazon|AZID=B017L2M7SW|AZN=HMB Powder}}
=References=
<references>
<ref name="JensenCaruso1989">M. D. Jensen, M. Caruso, V. Heiling, J. M. Miles, Insulin Regulation of Lipolysis in Nondiabetic and IDDM Subjects, Diabetes, volume 38, issue 12, 1989, pages 1595–1601, ISSN [http://www.worldcat.org/issn/0012-1797 0012-1797], doi [http://dx.doi.org/10.2337/diab.38.12.1595 10.2337/diab.38.12.1595]</ref>
<ref name="wada">wada-ama.org !!work!!, 6 December 2019 !!access-date!!, https://www.wada-ama.org/sites/default/files/resources/files/cas_2008_a_1510_despres.pdf</ref>
<ref name="StoutFukuda2015">Jeffrey R. Stout, David H. Fukuda, Kristina L. Kendall, Abbie E. Smith-Ryan, Jordan R. Moon, Jay R. Hoffman, β-Hydroxy-β-methylbutyrate (HMB) supplementation and resistance exercise significantly reduce abdominal adiposity in healthy elderly men, Experimental Gerontology, volume 64, 2015, pages 33–34, ISSN [http://www.worldcat.org/issn/05315565 05315565], doi [http://dx.doi.org/10.1016/j.exger.2015.02.012 10.1016/j.exger.2015.02.012]</ref>
