Monthly Archives: January 2019

The endurance athlete’s guide to fueling and weight loss part 1: fat and carbohydrate intake and storage

As some of you know, I radically changed my eating and fueling strategy a couple of years ago, and some of my friends have asked me for details.

The biochemistry is complex so there’s going to be a fair bit of science before I get to any advice. If you want more details, you can start with the chapters about fat and carbohydrate metabolism in Marks Medical Biochemistry, but I’ll warn you that biochemistry is really complex.

I guess I should also warn you that what I’m going to say is likely going to be at odds with what you have heard in the past. It certainly was when I first learned it.


Carbohydrate Fat Storage Asymmetry

The thing that has the biggest impact on this whole topic is a very simple topic, the difference in storage between fat and carbohydrate.

Fat

I’ll start with fat, because that’s the simplest one. Your body can store lots of energy as fat, and it stores it quite efficiently. When we eat fat, we are eating triglycerides:

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Triglycerides are simply 3 fatty acids hooked to a glycerol backbone. The fatty acids are just chains of carbons with hydrogens attached to them and then what’s called a hydroxyl group (pink in the image) at one end. Discussion of fats is imprecise; sometimes we talk about “fats”, sometimes “fatty acids”, and sometimes “triglycerides”. You can treat all those as equivalent for this discussion.

After digestion, fatty acids end up in the bloodstream, our adipose (fat) tissue pulls them in, and stores the fatty acids away. Very simple and the system works quite well.

The amount of energy you can store in fat cells is close to unlimited.

Carbohydrate Digestion

While the fat system is well-designed, the carb system feels like it’s jury rigged. Unlike the fat system, where all fatty acids are treated equally, the different sugars are treated quite differently.

Glucose

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Glucose is one of the common currencies for energy in the body. When you eat glucose, it is absorbed into the bloodstream. I’ll talk about storage in a bit.

Starch/Maltodextrin/Dextrose

These are generally what are known as “glucose polymers”, which is a fancy way of saying “chains of glucose”. The chains are broken apart by an enzyme known as amalase and there is some amalase in saliva; that is why if you chew a cracker for a long time, it starts to taste sweet – the starch which is not sweet has been broken down into individual glucose molecules and those taste sweet. There is a lot more amalase in the digestive system, so it tears all of the chains apart into individual glucose units.

You can treat dextrose, maltodextrin, and most starches as if they were glucose from a digestive perspective. Exceptions are what is known as “resistant starch”, which doesn’t get digested easily and can be converted to fat in the digested system by bacteria, and a cool product known as SuperStarch that I’ll talk about in a later post.

Sucrose/Fructose

Sucrose is a disaccharide, which means it’s a compound of one molecule of glucose and one of fructose. You can treat the glucose content just like any other glucose molecule.

The fructose is more complex. Some fructose may get digested into fat in the digestive system, but the fructose that makes it into the bloodstream cannot be used directly by the cells of the body. Rather than waste that energy, the liver takes the fructose molecules and breaks them apart. If glucose is rare (blood glucose is not high), it will become glucose, and if glucose is common, it will convert that fructose into fatty acids, which is released (if you are lucky) or accumulates (if you are not lucky). More on that later.

High fructose corn syrup is about 55% fructose and 45% glucose, so it’s pretty close to the same mixture as sucrose and from a dietary perspective, you can treat it the same.

I should also note that some people have varying degrees of fructose intolerance; it can cause what is politely known as “digestive issues”. If I eat any fructose during exercise I will get immediate stomach issues.

Lactose

Lactose (milk sugar) is another disaccharide, in this case a combination of glucose and galactose. The glucose is like any other glucose, the galactose is like fructose in that it can only be handled by the liver.

Alcohol

What we call ‘alcohol’ – ethanol – is lumped together with other carbohydrates even though it is not a sugar. Ethanol can only be metabolized through the liver, and like fructose and galactose, it might end up as glucose or it might end up as fatty acids.

Blood glucose levels and glucose storage

The range of healthy blood glucose levels is small: too little (hypoglycemia) and you get tired, cranky, sleepy, and in extreme cases can fall into a coma. Too much (hyperglycemia) and you get the downsides of type II diabetes. And perhaps surprisingly, there is very little glucose in the bloodstream – only about 4 grams at normal blood sugar levels. The body therefore has significant machinery to try to keep blood glucose levels within the healthy range.

Blood glucose level is regulated by the pancreas. As the body uses blood glucose, the level drops, and when blood glucose is low, the pancreas releases the hormone glucagon, and that signals the liver to release some of its stored glucose into the blood stream to bring the blood level back to normal. The liver can store about 100 grams (400 calories) of glucose, which it has stored as glycogen. If the liver glycogen stores are chronically low – if you aren’t eating many carbs – the liver can make glucose from other compounds – like lactate, the glycerol from triglycerides, and some amino acids from protein – using process known as gluconeogenesis.

If you eat something with carbs, as they are digested you will end up with glucose coming into the bloodstream. If the rate at which the glucose comes in is higher than the rate you are burning glucose, blood sugar will go up, and since it takes only 4 grams of glucose to double blood sugar levels and those pancakes and syrup have 50 grams of glucose, your blood sugar is going to skyrocket if nothing is done.

The pancreas detects the raised blood sugar, and starts releasing insulin, which is a signal to other tissues to do their best to pull glucose out of the blood. The liver will start pulling glucose in and storing it as glycogen, as long as it has space. The muscles will also start pulling glucose in if they have space to store it, and the muscles can store around 400 grams (1600) calories. Conversion from glucose to glycogen is quick and there are a lot of muscle cells, so if glycogen stores aren’t full, the glucose will quickly be pulled into those cells, and blood sugar won’t get very elevated.

At the same time, the insulin acts to minimize fat burn so as much glucose as possible is burned by the body.

Once the glycogen stores are full, the asymmetry shows up. There is no easy place to store the glucose but it’s still coming in from the digestive system, so the blood glucose level goes higher and the pancreas releases more insulin. There is only one place for this energy to go, and that is fat, so the liver and the fat tissue pulls in glucose and converts it to fat. This is slower than the conversion to glycogen, so the elevated blood sugar and insulin levels persist for a few hours.

I should note here that muscles are a bit weird; they can take in glucose as glycogen but they cannot convert glycogen back to glucose to release it to the bloodstream. That means that you can have low liver glycogen levels even if your muscles are full of glycogen.

The outcome is that even if you eat a very low fat diet, the glucose that can’t be stored in your glycogen stores is stored as fat, and until it is all converted to fat, you won’t be burning fat.

The previous explanation is how it works if you are metabolically healthy – if your cells are sensitive to insulin. If you are insulin resistant, then it takes much longer for your body to pull the glucose out of the blood, and if it’s bad enough, you will have elevated blood glucose values all the time, which means you have type II diabetes.

Insulin resistance is complex and there is not broad agreement on the causes; I’ll talk a bit more about it future posts.

Protein Digestion

Protein has a very minor role in this topic, so I’m going to ignore it.


Countertop CAD CAM

One of the leftover tasks from a bathroom remodel is to put a countertop on one of the small storage cabinets:

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We originally were going to have somebody fab a piece for us, but it’s a small job and they never really got back to us. So, it sat like this for a *long* time, but now it’s time to get moving on it.

After considering marble, we settled on doing solid surface because I can fabricate it with the tools that I already own. A little research took us to solidsurface.com, where we found a nice leftover piece of countertop in a color known as “Oregano Sand”, which we hope will go well with the overall color palette. That won out over white because we already have a white toilet and sink. A 20” x 43” x 0.5” piece was $116.33, and since I’m going to do a built-up edge – so it’s a full 1” thick on the visible part – I also picked up a tube of adhesive that is mostly color matched to the color of the material.

The fabrication approach I had planned was pretty simple:

  1. Carefully measure the size of the base and add 5/8” on the sides and front.
  2. Cut the solid surface piece on the table saw to the exact dimensions needed
  3. Round the left and right corners.
  4. Notch the left-back part to fit around the door trim
  5. Glue on other pieces underneath the top with them sticking out a bit.
  6. Trim the new pieces with a router and a bearing string-cutting bit so everything matches
  7. Round over the top edge with a rounding over bit.

The downside of this is that I’ll need to be doing some cutting on the table saw, and that’s not my most accurate tool, and I’ll likely need to do some sanding to clean things up.

I was also going to say that notching out the corner for the trim would be a big pain, but I just now realized that the cabinet is only held in place by two screws into a stud, and it would be absolutely trivial to slide the thing over to the right by 5/16” and eliminate the notch.

But anyway, I don’t like doing the big things on the table saw.

And then I realized that I could easily just do a CAD design for the countertop and cut it out on my shaper origin. That will give me very good tolerances and there’s no reason to expect that it won’t require less rework than the table saw, and there’s much less chance I’ll slip and do something bad.

So, I went of and did some Fusioning, and came up with the following:

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A simple base that is the side of the cabinet, and then a counter on top with nice 1/4” rounded corners on the front and a little notch at the back. I’ll be getting rid of the notch since I decided to just move the cabinet over slightly.

I’m currently missing the pieces that will be between the countertop and the cabinet to make the edge thicker. I’m going to model them on top of the countertop as that will be simpler to do. It ends up looking like this:

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Note that there are three built-up pieces, each 3” x 19.25”. That allows them to overhang the front by 1/8” and overhang the sides by 3/16”.

Fabrication

I decided to use the shaper origin to do the fabrication:

IMG_9418

That solid surface stuff is *hard*, it’s a bit like working in hardwood. I ended up only cutting 3mm at a time.

In retrospect, the shaper wasn’t the best choice for this; the size was fine but the edges weren’t as smooth as I had hoped. But they were close enough.

To do the layup, I needed the following items:

IMG_9423

The glue is a two-part color matched adhesive. And that presented a problem; the glue is in two parts, and they need to be dispensed in equal ratios. Real installers have nice guns (like caulking guns) that dispense both at the same time and run them through special mixing nozzles, but I didn’t want to buy a gun just for one use.

So, I built that little bolt thing that the knife is sitting on. I’ll open the tube and then use it to press the piston in the correct amount on each of the tubes, and then mix it together. Here’s what it looks like in use:

IMG_9425

This worked really, really well; both liquids are fairly fluid so it pressed out easily.

A large amount of color-matched (mostly) adhesive, a tiny bit of hardener:

IMG_9426

This stuff is really, really smelly; tons of volatiles; you want good ventilation and/or a good chemical mask. After a good mixing, I started spreading it onto the build-up pieces and putting them onto the big piece. This worked fairly well except that they want to slide sideways.

And then it was time for lots of clamps:

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Closeup:

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Here’s the worst edge. Yes, it’s not parallel, no it’s not a problem:

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The buildup parts are trimmed to be the same as the big piece using a router and a bearing bit. This went quite well, and produced a lot of chips that were like the fake snow you see at Christmas.

Here’s a long edge. Wavy wavy wavy; that’s from the shaper not tracking perfectly. Nothing that a ridiculous amount of sanding won’t fix. I stuck with the random orbit because I didn’t want to risk worse gouges with the belt sander:

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Once all the sides were square, the edge was rounded over with a 1/4” roundover bit with a bearing:

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Then sanding, sanding, sanding to get rid of the ridges and sand out the scratches from the router table. Worked my way through grits, 80/100/150/220/320. Here it is mostly cleaned off:

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and installed on top of the vanity with clear silicone adhesive. The color looks quite nice against the accent tile.

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Clopay Pinchproof door hinge #1

When we first bought our house nearly 20 years ago, one of the first things we did was to replace a 20-year-old wood garage door with a nice sectional from Clopay.

This door used a proprietary design known as a “pinchless” design; rather than using a simple  hinge that attaches to the two parts of the door, they designed a hinge where the top part is attached to top door upper door panel, and then there are little arms that are attached to the lower panel with a steel pin. Each hinge is slightly different.

Over the years I’ve had a few hinges break; it’s really common for one arm of the hinge to come off of the little pin, which puts more pressure on the other side. Over time, that side will break, and the door will start working poorly, and the failure may cascade to other hinges.

I broke 3 or 4 hinges, and whenever that happened, bought a new hinge and replaced it.

Last month I found that another hinge had broken, searched online, and found out that Clopay has not only discontinued that design, they have stopped making replacement parts and. You can find some of the hinges available, but not the #1 hinge that I wanted.

I tried a jury-rig that rapidly failed, thought about a new door ($1000, no thanks), and then decided to fabricate one myself. My goal is to beef it up with slightly thicker sheet metal and make the arms that keep breaking wider.

Reverse engineering

To start, I need a design that I can work from, so I started by pulling the hinge off and making a pattern:

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From that I did a tracing to get the format, and got out the calipers to measure holes and other parts directly. Here’s what I ended up with:

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At this point, my first thought was to do a quick drawing, print it out, and just transfer it to a piece of sheet metal – somehow – and then do the machining to create the piece.

I’ve done that sort of thing in the past, but the problem is that it’s hard to get the layout right, and if you mess it up you can easily ruin a lot of work. Is there a way to make it more foolproof?

CAD

The obvious solution is to do what I would call a real design. So I sat down with my drawing, a ruler, and calipers, and fired up Fusion 360.

First off, I draw the outline as two separate bodies.

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This is pretty close, though the end of the arm is square rather than rounded. I wanted more beef on the arm, so I’ll add that in next:

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Throw in some filets, join the old and new parts together, and we get the following:

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Now we need some holes:

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The locations of the holes are pulled from my drawing, and the sizes come from direct measurement of the holes in the current hinge. The little tab on the hole in the arm is there because the pin that goes through has a little tab on it for retention.

Mirror across a plane in the middle, do some cuts, do some combines, and we end up with the following:

image

I then exported that to an SVG file using the Shaper Origin plugin for Fusion. You can find the SVG here.

Manufacturing

I took the design and printed it out, and then put it behind my traced design and held them up to the light to verify that things were in the right place.

The next task was to transfer that design to metal. The way that real machinists do this is to put layout dye on the metal and then scratch the design onto it. I don’t happen to have any dye lying around nor am I experienced at this.

But I do have a laser cutter. Steel is very reflective of infrared so I can’t mark it with my laser cutter, but maybe there is something I can put on it that I can ablate away?

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So, I grabbed a sharpie, applied it to a large enough area, and went out to the laser cutter to see if I could ablate it away.

It was an absolute failure, even at powers that would easily cut 1/8” wood. Not enough IR absorption to work.

So, I grabbed a can of black spray paint I had, went outside, and put a nice easy full coat on the steel. And then put it in from of a heater to dry:

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Then a few tests, and even at 25% power and my fastest speed, it still worked well:

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and ran the drawing:

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Machining

First, I cut off the part with the design and scraped the hell with the base of my jigsaw:

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I cut the holes incrementally, starting at 1/16” and working my way up. I high recommend drilling them from the back, since if you drill them from the front the shaving will scratch off a lot of the paint.

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Next, I cut the outline with the jigsaw. I also scribed on some bend lines that I will need later:

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Starting to actually look like the drawing. I drilled a starting hole in the waste in the middle bottom, cut out the long sections with a jigsaw, and then rounded off the pieces with a grinder:

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A bit more cleanup with an angle grinder and a dremel, and we end up with the following:

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A couple minutes to fold the bracket and pull off the old one:

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The final step is to take the tubular mount of the wheel and move it from the old mount to the new one. The tube is flared out; I unflared it by pounding it on the vice and then expanded it back out with a flared socket adapter. If I had a copper tubing flarer, that would have been a better choice. And, we’re done:

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And the quick reinstallation:

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On the left side you can see the end of the pin sticking out.


Review: MITx: 16.885x–Engineering the Space Shuttle

This fall I decided to spend some of my free time doing something different, so I signed up for an Edx/MITx online course on the Space Shuttle.

It was fascinating. If you have any interest in the details of how the Space Shuttle from an engineering standpoint, you will love this course. The course is run/hosted by former astronaut and MIT professor of aeronautics and astronautics Jeff Hoffman, and wherever possible the actual lectures are done by ex-shuttle engineers or managers. Main engines? Lecture by J.R. Thompson, manager of the Main Engine Projects office at Marshall. Flight control system? Phil Hattis, one of the leads on the system. Mission control? Wayne Hale, flight director for 41 missions. Saturn and shuttle? Chris Kraft.

A brief overview:

Section 1: How the Space Shuttle was Originally Designed and Approved

  • Lecture 1: Origins of the Space Shuttle – Dale Myers
  • Lecture 2: Development of the Space Shuttle – Aaron Cohen
  • Lecture 3: Early History of the Shuttle and NASA’s Relationship with the Military – Bob Seamans
  • Lecture 4: Political History of the Space Shuttle – John Logsdon
Section 2: Space Shuttle Sub-Systems
  • Lecture 5: Introduction to Space Shuttle Orbiter Subsystems – Aaron Cohen
  • Lecture 6: Orbiter Structures & Thermal Protection System – Tom Moser
  • Lecture 7: Space Shuttle Main Engines – J.R. Thompson
  • Lecture 8: Space Shuttle Aerodynamic Design – Bass Redd
  • Lecture 9: Aerothermodynamics – Bob Ried
  • Lecture 10: Space Shuttle OMS/RCS APU/Hydraulics – Henry Pohl
  • Lecture 11: Thermal Control and Life Support System – Walt Guy
  • Lecture 12: Mechanical Systems and RMS – Alan Louviere
  • Lecture 13: Shuttle Flight Control System – Phil Hattis
  • Lecture 14: Systems Engineering Review, Matrix Management, and Cost Estimation – Aaron Cohen

Section 3: Operating the Space Shuttle

  • Lecture 15: Space Shuttle Training and Mission Description – Jeff Hoffman
  • Lecture 16: Payload Operations and Systems Engineering – Tony
  • Lecture 17: Space Shuttle Launch Operations – Bob Sieck
  • Lecture 18: Space Shuttle Abort Modes, Payload Bay Doors, EVA – Jeff Hoffman
  • Lecture 19: Mission Control – Wayne Hale
  • Lecture 20: Test Flying the Space Shuttle – Gordon Fullerton
  • Lecture 21: Columbia Accident – Sheila Widnall
  • Lecture 22: Hubble Space Telescope and the Space Shuttle – Jeff Hoffman
  • Lecture 23: Apollo and the Space Shuttle – Chris Kraft
  • Lecture 24: Retrospective on the Space Shuttle – Jeff Hoffman/John Logsdon/Wayne Hale


Tell me more about trans fats…

Trans fats are fats which have a specific chemical structure…

Saturated fats are called “saturated” because they have as much hydrogen in them as possible, so they are very simple structurally; just like a long column. Because of that, they fit together very nicely and that is why saturated fats tend to be solids at room temperature.

This picture shows three fatty acids; the top on is saturated, and notice how it is nice and straight.

Unsaturated fats have fewer hydrogen molecules; at specific places in the chains of carbon atoms there are missing hydrogen atoms. Monounsaturated fats have one spot, polyunsaturated have two or more. The connections between those carbon atoms become what are called “double bonds”. One of the features of double bonds is that they are easier to break; that is why unsaturated and especially polyunsaturated fats go rancid easily, and that is why there is concern with using them for deep fat frying; those bonds can be broken, the broken parts can be oxidized, and you end up with a nasty compound called an “aldehyde”.

Because of the physics of how things work, there are two ways that double bonds can occur. The “normal” way – the way that is found in the majority of unsaturated fatty acids – is what are called “cis” bonds. These bonds are at an angle, so unsaturated fats have one or kinks in their structure; see the middle fatty acid, which has two double bonds. Because of that kink, they don’t fit together very well, so they are liquids at room temperature.

Where the first double bond occurs matters biologically; that is described by counting the number of carbon atoms before the first double bond, and that is known as the “omega” number. If we look at the picture, we will see 6 carbon atoms before the first double bond, so this is an omega-6 oil.

Trans fats

The fats that are produced by plants or animals are either saturated fats or unsaturated fats with cis bonds; that is why I called it the “normal” way.

But there is another way that the double bond can occur; it is called a “trans” bond, and that is where the term “trans fat” comes from. Instead of a big kink, there is just a little jog in the structure. This turns out to be important biologically.

There are some natural trans fats; it turns out that there are bacteria that can produce trans fats. These bacteria live primarily in ruminant animals, which means that if you eat dairy products like cheese or the flesh of ruminants, you will get some trans fats. It is not clear where the natural trans fats are problematic or not, but the research I’ve seen suggests that the answer is “probably not”.

Which takes us to artificial trans fats. Producers of polyunsaturated vegetable oil wanted to expand their markets so they could sell more, but the usages of the oils were limited because they were oils. It was discovered that if you heat up polyunsaturated oils under high pressure where there is a lot of free hydrogen, you can “hydrogenate” them and make them more saturated. If you fully saturate them, you just end up with a saturated fatty acid that is the same as a saturated fat from plant or animal sources.

But, if you take a polyunsaturated oil and partially saturate it – partially hydrogenate it – it turns out that some of the remaining double bonds will flip from “cis” to “trans”, and you have an artificial trans fat. Which is pretty bad.