(that’s the way we like our gluc)

If you care about peak cognition, care about your glucose. It’s not just your A1c on a lab slip that matters - what your blood sugar does across a day and what your body weight does across a year also factor into your ability to focus. This is a brief post on recent research about how blood sugar impacts your cortical function.

Let’s start with the current belles of the ball: glucagon-like-peptide-1 agonists. A new meta-analysis pooled 18 randomized trials of GLP-1as in type 2 diabetes and found real cognitive impact with steady use. On global screening tests, scores edged up: +1.33 points on the MMSE and +1.70 on the MoCA. More importantly, when treatment extended  ≥24 weeks, the pooled effect size for cognition landed around 0.8 SD - pretty big for this domain.¹ This isn’t exactly the pill from Limitless, but it’s not a throw-away result by any means. It says: sustained GLP-1RA therapy moves cognition in the direction you want. Is it the blood sugar control, the weight loss, some other confounding factor that GLPs do? Unclear, but my guess is the regulation of blood sugar that these attain rapidly along with improvements in weight and other metabolic markers.

But medication isn’t the only lever (see the recent Attention, Please post: “Shuffle the Pups” for more color here). Exercise has repeatedly been shown to work as well for cognition, and it doesn’t require prior authorization or thousand dollar copays per month. It works for people who are metabolically healthy (focused on in the above article), but also in folks with dysregulated glucose metabolism.  In older adults with T2D, a 2024 meta-analysis reported a standardized mean difference ~0.65 for global cognition with exercise interventions.² Four sessions per week, mix of aerobic and resistance, gets you most of the way there. To put this in context of what controlled psychostimulants yield when taken by normal populations (i.e. adults without ADHD), you get an effect size of around 0.2 for methylphenidate, lower for modafinil (0.12), and nil for amphetamine (see: Stimulants Without ADHD - Working Harder, Not Smarter).

Diet also, obviously, plays a massive role here as well, both short and long term. It shows its influence on your focus in the hour after a meal and in the years after you change how you eat. In a well-designed crossover trial, adults with T2D ate a low-glycemic diet versus a high-glycemic diet. Pre-lunch, the low-GI diet produced better global and executive performance. Modest, not mind-blowing, but moving results in the direction we want – right before you sit down to do the thing.³ Over years, a Mediterranean pattern (a diet which is fine, but I’m not enamored with though it’s always used in these studies) tracks with slower decline in global cognition for people with T2D; each notch higher on the adherence score predicted a small positive shift in a composite of cognitive tests over two years (β≈0.03 SD per unit).⁴ Small, positive dietary changes compound over years - much in the same way that poor dietary choices corrode cognition over time.

Glucose stability also matters independent of averages; the fluctuations in glucose after a meal are commonly referred to as “excursions.” In a large meta-analysis, high glycemic variability was associated with a 38% increased likelihood of developing Alzheimer’s Disease. You don’t need ascetic monk-level self-control; you need less volatility.⁵ Fewer, lower spikes of glucose (and insulin) lead to better thinking in older age.

Weight loss is the final variable worth covering here. Meta-analysis after bariatric surgery shows improvements across memory, attention, and executive function over 3–12 months. Effect sizes vary by domain and study, but the direction is consistent: lighter weight often means clearer thinking.⁶ And outside of surgery, GLP-1RA monotherapy has trial data beyond glucose: in a randomized study of obese people with prediabetes/early T2D, liraglutide improved short-term memory z-scores (about +0.8 SD within-group). That’s a result big enough to matter, and you also get to look better in your jeans.⁷

So what is the takeaway here?

If you’re on a GLP-1a already for metabolic reasons, treat cognitive benefits as a bonus that shows up after the six-month mark. You aren’t going to start a GLP for focus - but just like with the improvement in cardiac health on GLPs, these drugs improve a lot of things (or maybe metabolic dysfunction just messes up a lot of things these medications repair). The early weeks of treatment are more about the scale (weight loss and food intake changes) and the CGM trace (reducing the baseline sugar and peak excursions); the later months are where the 0.8-ish cognitive effect size emerged in pooled analysis. That’s a reason to prioritize adherence for a timeframe beyond when the most robust weight loss effects often take place.¹

If you’re not on a GLP-1a, and you’re a bit metabolically disrupted, you still have two high-yield moves:

• Exercise like a big boy or girl. Three to five days a week targeting 45-90 minutes per session. Mix Zone-2 aerobic work (can do it while talking with effort or complete the exercise purely nose breathing) with progressive resistance training (a few sets to near-failure at whatever reps are necessary to get you there). It will take twelve weeks minimum before you should judge results - but I can promise you, you will feel better well before that if you are diligent. Expect a medium lift (≈0.6 SD) in global cognition if you’re starting from low baseline activity.²
  

• Lower the post-meal glucose spike amplitude, especially in the morning. Swap the toaster-pastry-and-fruit-juice pattern for protein, fat, and fiber; pick low-GI carbs. You don’t need to become a feral carnivore,  just eat in a way that provokes smaller excursions. Expect small-but-steady gains in attention/executive function.³
  

Over months to years, a Mediterranean-leaning pattern is a safe bet. I don’t find the diet itself to be magic, it’s basically just shifting away from the Standard American Diet (SAD) of high fat/sugar, high fried foods and calorie excess. You don’t need a cleanse. It’s vegetables, legumes, olive oil, fish, fewer ultra-processed “foods,” and minimizing alcohol. Expect small annual cognitive bumps that compound.⁴ If all you can do is cut out eating refined sugar in every meal, this will help. And please remember, fruit juice is NOT healthy.

And keep your glycemic variability in check. Excursions on cruises to the Bahamas are fun. Excursions on your blood sugar should be avoided. Even if your average A1c looks fine, jittery control punishes your brain over time. The target is boring traces and fewer massive swings, which will also help keep your insulin surges in check and lead to less frequent need for midday siestas.⁵

Nothing in this post is meant to pretend glucose control is easy or habit changing can be done with a weekly subcutaneous injection. These interventions will not double your IQ. We’re talking about reclaiming a few minutes per hour where your brain does what you ask without protest: holding a thread of thought, task switching more smoothly, remembering what you read on page two when you reach page ten. These are small-to-medium effects, repeated daily, and can add up to a dramatically altered career arc if followed faithfully. Or you can stick with eating dessert three meals a day (what else could you call Frosted Flakes or Pop Tarts?) and just sort of accept your brain is being attacked as much or more than your waistline.

If you want a simple place to start, try this:

• Morning: Breakfast built around protein + fiber + low-GI carbs. (Think eggs + greens + oats or Greek yogurt + nuts + berries.) Don’t poison yourself with simple sugars before you’ve even gotten the machinery going. Then get in 30 minutes of Zone 2 before your first deep-work block. Nose-breathe throughout, brisk walk or light ride on the stationary bike. You might work up a little sweat, but let’s be honest, you’re probably working from home and no one will notice.
  

• Midday: Prioritize protein, fill with fat, skip sugar. Do you see how that mnemonic works? Walk again after lunch. If you lift today, keep it 30–45 minutes, push to near-failure, not actual failure. No heroics; steady progress beats theatrics and prevents injuries.
  

• Evening: Limit alcohol with dinner, skip the third cookie. This doesn’t mean no indulgences, just don’t make indulgences the norm. Consider a few body weight squats or another easy walk after your last meal to pull in that glucose to the muscles. You brain will thank you.
  

The summary is simple: lower glycemic chaos + less fat mass + more fitness = a better brain. 

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References

1. Wan S, Yan H, Sun Q-Y, Zhu J-Q, Wang H-H, Qu K-Y, Yi X. Effects of GLP-1 receptor agonists on cognitive function in patients with type 2 diabetes: A systematic review and meta-analysis based on randomized controlled trials. Diabetes, Obesity and Metabolism. 2025 Oct 17. Online ahead of print.
   

2. Lu HH, Tang ZY, Xu S, et al. Meta-analysis of the effect of exercise intervention on cognitive function in elderly patients with type 2 diabetes mellitus. BMC Geriatrics. 24, Article number: 770 (2024).
   

3. Grout M, Lovegrove JA, Lamport DJ. A multimeal paradigm producing a low glycemic response is associated with modest cognitive benefits relative to a high glycemic response: a randomized, crossover trial in patients with type 2 diabetes. Am J Clin Nutr. 2023;117(5):859-869.
   

4. Mattei J, Bhupathiraju SN, Tucker KL. The Mediterranean diet and 2-year change in cognitive function by status of type 2 diabetes and glycemic control. Diabetes Care. 2019;42(8):1372-1380.
   

5. Chen J, Yi Q, Wang Y, et al. Long-term glycemic variability and risk of adverse health outcomes in patients with diabetes: A systematic review and meta-analysis of cohort studies. Diabetes Res Clin Pract. 2022 Oct;192:110085.
   

6. Tao B, Tian P, Hao Z, et al. Bariatric surgery improves cognitive function in patients with obesity: a meta-analysis. Obesity Surgery. 2024;34(3):1004-1017.
   

7. Vadini F, Simeone PG, Boccatonda A, et al. Liraglutide improves memory in obese patients with prediabetes or early type 2 diabetes: a randomized, controlled study. International Journal of Obesity (London). 2020;44(6):1254-1263.