Origin of the 30 carb meal thing

I just read the book that JDRF gives away called Bright Spots and Landmines. In this book the author talks about keeping your carbs under 30 each meal for good control. I’ve also heard this 30 carbs from TCOYD videos and a couple other places that I can’t remember at this moment.

My question is does anyone know where this dumb rule comes from? I’ve read or heard about it so many times that I’m wondering if there was some kind of large scale meal time insulin study in the past.

BTW whenever anybody mentions 30 carbs they never say whether it’s net or total. No mention of gender or age either. I guess less than 30 carbs is perfect for just about everyone all the time.

I’d say do what works for you and your control goals.


This article summarizes a few studies of diets with varying amo7nts of carbs but basically recommends that each person has to figure out what works best for him/her/them.


I am with @jim26, do what works for you. As to carbohydrates, my experience is to bolus for net carbs plus 50% of fiber carbs. In theory net carbs should be all that is digestible, but there is digestible and indigestible fiber. I don’t think the labeling takes that into consideration.

Soluble vs. insoluble fiber

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There are 2 different types of fiber – soluble and insoluble. Both are important for health, digestion, and preventing diseases.

  • Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. It is also found in psyllium, a common fiber supplement. Some types of soluble fiber may help lower risk of heart disease.
  • Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains. It adds bulk to the stool and appears to help food pass more quickly through the stomach and intestines.

Evidently there is no requirement to differentiate between soluble and insoluble fiber on a nutritional label unless they make specific health claims. Sounds like a loop hole to me. I couldn’t copy and paste this text, so here’s a screenshot.



I always supposed it came from the observation that the smaller the meal bolus, the smaller the error in dosing, which means smaller excursions. This concept has been independently rediscovered many times, and was popularized by Dr. Berenstein who advocates an extreme low-carb diet as a way to get the A1C of a non-diabetic. Some people insist that’s by far the best way. Many people agree. I’m towards the carb-heavy end of the scale and get A1Cs in the mid to low 5s and good time in range on the AGP report. There’s truly no universal recommendation on low-carb or not, it’s really about what works well for each individual; considering health, effort, convenience, and emotional factors.


I am having difficulty finding any such recommendation for either type 1 or 2 diets. Richard Bernstein is on a 10 gram carbs per meal for a total of 30g/day. I do think 90 to 100 grams of carbs over the day is doable. I was only able to do the extreme carb restricted diet of Dr. Bernstein for about 6 months which enabled me (a type 2) to stop Micronase.

I consume about 41 grams per meal for 123g daily total.

This is an interesting paper from 2019 on the subject:

It goes into the pros and cons of low and high carb diets for type 1 diabetes. One issue with high carb diets is the risk of metabolic syndrome and weight gain. The paper doesn’t use the term double diabetes, but if a type 1 has the genetic variants for insulin resistance they can be both autoimmune type 1 and insulin resistant type 2. These gene variants are not rare.

Anyway if you have some links to the 30g carb/meal, please post them, Thanks.


I think the whole discussion of low carb vs moderate/high carb is confused by definitions. Here is what the linked paper above uses to define, Table 1 for the general population:

Table 1

Suggested definitions for different carbohydrate diets based on values from Feinman et al. [28] and Seckold et al. [34].

Diet Recommendation
Very low carbohydrate diet 20–50 g per day or <10% caloric intake or <1 g/kg bodyweight/day
Low carbohydrate diet <130 g per day or <26% total energy intake or <3 g/kg bodyweight/day
Moderate carbohydrate diet 26–45% of total energy intake or 3–6 g/kg bodyweight/day
High carbohydrate diet >45% of total energy intake or 7–8 g/kg bodyweight/day
ADA guidelines [42] 45–60% total energy intake from carbohydrate

So, for a 175 pound person (me), less than 3g of carbs per kg of body weight is 240 grams of carbs per day…anything below that defines my diet as “Low carb” according to the paper. I am usually at around 200 grams of carbs per day putting me at less than 3 g/kg of body weight. The authors would classify my diet as low carb. I have no idea if the definitions in Table 1 of the paper are settled science or ??..but I am way in excess of the 30g per meal discussed by the OP and somehow still defined as Low carb.


Thank you for all the replies! I’m going to read the articles that CatLady and Carlos linked to!

just thought it was strange that I kept hearing this 30 carb thing. I almost think that the Bright Spots author pulled that number out of his you know what. Then he started writing about it on Diatribe and others copying it. I’ve seen it on their website a lot.

I am in no way limiting carbs. I use the net not total and it’s always worked for me. It seems like we all dose for what we learned first - either total or net.


Thanks for the table John! That’s interesting because low carb seems to have multiple meanings to the general public.

I would be describe my self as medium carb because I eat around 140 net a day. It feels like a good satisfying amount.

When I started insulin I read Bernsteins book and followed the whole ultra low carb for 6 months but that was out of fear. It certainly put me in a nasty mood. After a few months on Dexcom/Omnipod and lots of studying insulin I got back to my normal diet.


Ha, did you see Table 2 in that paper (daily carbs for athletes)? The daily carb numbers are sky high. Even though I am not in the same league as a true athlete, I have had plenty of days at “moderate” or “High” levels of activity…the authors would have me eating up to 800 grams of carbs on those high activity days? Even the light activity would have me at 240 to 400 grams per day. Seems crazy to think about numbers that high.

Table 2

Guidelines for carbohydrate intake by endurance trained athletes, adapted from Burke et al. [43] and the position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine guidelines [38].

Level of Activity Carbohydrate Targets
Light (low intensity or skill-based activities) 3–5 g/kg bodyweight/day
Moderate (approximately 1 h per day) 5—7 g/kg bodyweight/day
High (e.g., 1–3 h moderate to high-intensity exercise) 6–10 g/kg bodyweight/day
Very high (e.g., >4/5 h of moderate to high-intensity exercise) 8–12 g/kg bodyweight/day
Extreme (e.g., elite cycle competition) >12 g/kg bodyweight/day

800 grams sounds like a fun day if no injected insulin is needed. If there ever is a cure I might try it out for a day. I’m thinking big Açaí bowls for breakfast and lunch then sushi for dinner followed by dessert my high school favorite Coke Slushy. Plus a Pumpkin Spice Latte and Bagel for a snack. :grinning:


I was trying to find what the average daily carbs the members of Team NovoNordik eat when training and racing. All I could find is the on bike fueling of 40 to 60 grams/hour. But I know for a fact that they will have to replenish glycogen in the hours off bike. Otherwise they will go extreme hypo.

Continuing with this tangent, endurance events will deplete skeletal muscle and liver glycogen in a few hours. That’ll require some 600 to 800 grams of carbohydrates. The muscles will take up any available glucose out of the blood without insulin.

Here’s another link from an endurance runner.


I don’t listen to the carb rule although I like that book. He has an email with good information that I get a few times a week. As for total vs net carbs I never subtract fiber. I found makes no difference to me so I bolus for the total amount listed.

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