Sugars vs Starch, what is your approach?

Before I ask this to my dietician, I’d like to hear the opinion from the experts here. As many of you, I have multiple goals regarding nutrition:

  • Improve body composition
  • Improve lipids profile
  • Support work on the bike

The only potential point of conflict between these goals is the consumption of simple sugars. I understand the importance of fueling the work and the speed of an absorption….so I can see 2 ways of going about this:

  1. Eat super clean off the bike, only complex carbs and fuel your workouts with sugar.

  2. Eat super clean off the bike, only complex carbs, but add more of these to pre load for the bike work so you minimize the amount of sugar needed on the bike.

Asume both approaches have a 40-45% carbs (starch, sugar, fiber) weight in the diet. The only difference is the proportions of complex vs simple.

I want to hit the sweet spot between “health” and “performance” as I enter the golden years.

Some info about me:

270w FTP
20% Body Fat

I like carbs on the bike. They reduce RPE for me.

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  1. All of the above

Based on what I’ve read, option 2 is fine for shorter workouts. You need option 1 for longer rides.


Option 2a is the hybrid option. I only use sugar on 3+ hour hard group rides or during a big kj burning workout. All other rides are fueled with regular food, oatmeal/cereal before, a banana or two, a granola bar, and occasionally all of the above with some drink mix in the bottle. I’ve taken peanut butter sandwiches on 5 hour gravel rides even.

There’s a huge middle ground between ‘sugar is evil’ and ‘100g per hour for every hour of training’.

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I think there are a few things to unpack here.
firstly though starch ( amylose type since there are more than one type of starch) will start to be broken down by amylase in the mouth and in essence becomes glucose very rapidly. What I think you mean is fast carbs, like sugars and some starches and slow carbs like some fibers etc. You can tell the difference by the glycemic index. That is how fast they convert to sugars in the blood.

Your body stores a limited amount of glycogen which gets used when sugar is needed and not enough is available because it is being used up too fast. So again this is complicated topic. At certain levels of effort your body can actually burn fat, when the rate increases past at certain point then blood sugars are needed. if they can not be absorbed then they typically come from glycogen.

So the concept of loading relates to topping up the glycogen stores. But as said this is limited.

You can not breakdown most true complex carbs known as fibers until they hit the large intestine and the bacteria go to work. Then you only get a bit the rest is used by the bacteria and that is why the caloric content of fiber tends to be around 2 cal/g vs basic carbs like starch and sugars are 4 cal/g…

You can do things to manipulate the burning of calories but ultimately it is sugars that are the fuel.

However the rest of your day eating a good balanced diet that limits processed sugars and high caloric things processed with added sugars is a good thing.

So I am maybe missing the point of your question but what it is not what you eat before hand that leads the story, it is how intense your workout and the duration that you fuel for. Dr Alex Harrison can give you a really good run down of what good fuelling looks like, both before you workout, daily as well as during different workout situations.


I’m 3 days into wearing a CGM. I’m not a diabetic but I have a family member who had it for pregnancy and gave me it to use for the last month of the script.

I did a easy endurance ride yesterday and it caused my blood sugar to be in the ‘fasted’ state for a few hours post exercise, with a very quick glucose spike when I refueled after the workout (no carbs on the bike).

I just did a very intense session today (think vo2 type) and despite fueling on the bike with malto/fructose, my glucose dropped to hypoglycemic levels. It has stayed in a low-fasted state for the past few hours afterwards, despite large carb rich meals.

All that said, I wouldn’t worry too much about taking sugar if you are training hard, but skip it for ‘recovery rides’. I’m going for a longer endurance ride tomorrow (hopefully) and will take 40g/hr sugar and could report back.

I was a real doubter of sugar while on the bike, but with this data, I see that if you’re really smashing it on a ride, you could prob take 90/hr and still be hypoglycemic. Very enlightening. Also, key word is smashing it (like race efforts of SS or higher work.

Lastly, from these few days with the CGM, I see that timing of eating is super huge. You basically don’t want to eat anywhere close to bed, or have a large meal before bed. We really have it backwards with dinner being the biggest meal. I’ve been above a fasted state for the past 2 nights, only got back down after I work up and started moving again. I pretty much aleast eat clean, but in large portions. I’m in my early 30s.

I’d go with option #1


I’m not sure you can make conclusions like not eating before bed. These devices are meant for diabetics not for people with normal blood sugar responses.

Healthy people wearing CGMs basically get pushed towards a low carb / low glycemic index diet because they get an alarm every time their blood sugar rises.

Not necessarily. I injested 550g of total carb today (a large amount). I never went over a blood sugar spike of 140g. However, when I ate a large portion of carb close to bed, my blood sugar did not return to fasting for about 6-8hours (in the absence of a very intense workout like today). Compare this to eating a similar meal during the day where the sugar is taken up by skeletal muscles in motion and I return to fasting within 90 minutes (not exercise per se, just not sleeping in bed). In this instance, the CGM just provides evidence to support the mechanism behind how healthy develop T2D (insulin insensitivity) through sustained BG above fasting levels.

I’m not going to eat less carbs but I’m considering timing dinner earlier. I eat really clean and have for many years. But this brief glimpse into the data makes me realize the BG levels of the general population must be elevated almost all day and night. Totally not surprised so many people develop T2D or are ‘prediabetic’, etc. It must be almost impossible to eat enough to become overweight or obese and not have chronically elevated BG levels. Typically, insurance will only cover a prescription for a CGM to patients who are prescribed insulin, so data isn’t widely available outside of some researchers conducting studies (probably on already diabetics).

I agree that when you read the ADA recommendations for BG levels and you eat like an endurance athlete, they’ll say you’re prob a diabetic or have high likelihood of developing it. This advice isn’t adjusted for athletes or people who exercise a lot. Regardless, elevated BG all night prob isn’t what you want to have if you believe the current theories behind insulin insensitivity, etc.


Thanks for your answer. Would you expect body composition, lipid profile to be different in a thought experiment of 2 identical individuals that eat the same calories from carbs except one gets it from orange juice and the other from potatoes?

Well I can not say for sure, though I am certain there are people in metabolomics and physiology who have looked at these thing. The 1st thing to consider is that two people will be unlikely to process these foods the exact same. Secondly there are a lot of biochemical steps between any sugar being converted to any lipid component.

Now pose the question same person but consume orange juice vs potato… the first thing to consider is energy density of these two things. If orange juice was 10% sugar… then 100 ml would be 10 g sugar (40 cal)… in comparison it would take about 11.1g - 12.2g of potato (assuming about 80-90% solids for 10 g carb= 40 cal) so not a lot of potato (also potatoes are not just starch though mostly are, that is why during the storage they convert sugars to starch then back to sugars just before they are ready to sprout)…

Once consumed both go to sugars fast, but then there is the thing about juice, it is fructose and sucrose or only sucrose, thus a combo of fructose and ultimately glucose. Fructose I recall (correct me if I am wrong) gets metabolized in the liver while glucose goes straight to the blood. Starch is just glucose so there is that and potato is a high glycemic index vs juice. (78 vs 50) but that is because of the caloric density. So if isocaloric then I think they will end up darn close to one another in the end. I am sure if you search Pubmed you will find studies of this sort and see the metabolic impact. All really cool ideas but in the end of the day calories are calories and carb (sugars and starch) calories are just calories. If you consume more calories then you burn you do something with the excess and that something very much depends upon you genetics. I am a burner… I can eat and never gain appreciable weight while others can eat the same calories and end up gaining weight. This is a topic that has no really easy answers, the simple answer is “it depends”.

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Perhaps useful


This is the key to everything. I have some reason to believe that my phenotype is sensitive to carbs as it pertains to blood lipids.

I wonder if we really need “very rapid” carbohydrate sources if we are fuelling on a schedule and not depleting ourselves. Say we are consuming 30-40g every 30 mins while riding, would that not release quickly enough to prevent hypoglycaemia even with intense exertion if we were had appropriately fuelled in advance of exercise?

Not a diabetic but if I can get a pharma rep to give me some CGMs as samples I will definitely try one for myself, would be interested to see how different exercise intensities effect my blood sugar to better understand appropriate intra-workout nutrition.

Have you try apple cider vinegar before going to bed or with your last meal? It has shown to have an impact on blood sugar the next morning. If you’re going to make the experiment, let me know the results.