How does when you eat impact your blood sugar?

Blood glucose levels can spike and dip for dozens of different reasons, and as well as what you eat, it turns out that when you eat also impacts your blood sugar. The good news is, simple changes to your eating schedule can help you stay on top of your blood sugar levels.
Megan Carnegie
min read
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Quick summary

  • Nutritionists segment eaters into free-rangers, grazers, and repeat eaters, but typical mealtimes vary from house to house and country to country.
  • People with type 2 diabetes can help keep their blood sugar level more stable by creating a routine of regular mealtimes, with 4-5 hours between each meal.
  • Time-restricted eating can also improve your glucose levels and help with weight loss.
  • Skipping breakfast can wreak havoc on blood sugar levels for the rest of the day and research suggests a breakfast including healthy carbs could improve glycaemic control (unless you're experiencing the dawn phenomenon!).

What you eat is essential for managing type 2 diabetes - whether it’s through reducing your sugar intake, managing the amount you drink, or experimenting with a plant-based diet. The ultimate aim is to control your glucose levels. But what about when you eat? 

We all have different relationships with when we eat, which vary wildly depending on the day and what we’re up to. Nutritionists tend to segment eaters into three basic groups: the free-rangers, who grab whatever they can to eat whenever they can; the grazers, who nibble throughout the day rather than eating at set times; and the repeat eaters, who stick to three set meals a day. Not only do typical meal times differ from household to household, but country to country as well. Sitting down for dinner at 10pm in Spain, for example, takes a while for us Britons to get used to!

These styles of eating will land slightly differently if you have type 2 diabetes. The big dietary changes you might be making, or thinking about making are just one puzzle piece - an awareness of the impact of when you eat can also make a difference. Today, we’re diving into smaller schedule changes to help you along the way. 

Regular mealtimes

Skipping meal times as someone with type 2 diabetes is a big deal. It can lead to dangerous fluctuations in blood sugar levels and create further complications further down the line. When the hunger does strike, you’ll be more likely to reach for the calorie-dense foods that are quicker to prepare and not so great for managing diabetes. One study found that skipping meals to save calories sets the body up for fluctuations in insulin and glucose that leads to weight gain rather than weight loss.[1]

Eating regular, balanced meals will help to stabilise your blood sugars. [2] While people with type 2 diabetes are sometimes recommended to eat six small meals a day, researchers believe that three meals is better at controlling the need for insulin, and helping you lose weight. This is more attuned to your body’s biological clock too, as the body - after a long overnight fast - is optimised for eating in the early hours of the day, after fasting and sleeping in the evening and overnight.[3] So that means breakfast, lunch, and dinner with around four or five hours between each meal will keep your body fuelled evenly throughout the day.

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Avoid midnight feasting…

You may experience symptoms that disrupt your sleep - intense thirst or needing to go to the toilet, for example - and once you’re up, the glowing light of the fridge is a temptation that’s hard to resist. But munching late into the night, especially on foods high in carbohydrates, could send your systems haywire and make you feel overly warm, irritable, or unsettled in bed, as well as result in you waking with very high blood sugar levels. It can also contribute to weight gain. The same rule applies to post-dinner snacking too - which you could curb by brushing your teeth after dinner. Those biscuits? Not quite so tempting with a minty-fresh mouth. 

Have a think about whether this nocturnal feasting is driven by hunger or something else - perhaps it’s boredom, anxiety, or force of habit? Drilling down on the mental and emotional components sending you toward the fridge is the most effective way to make lasting change in your habits. One approach is to do something - take a stroll, read a book, or do something with your hands while you decide what your body needs. And late-night nibbles aren’t totally off limits - if you find you’re genuinely hungry, pick something high-fibre and low-sugar, like wholegrain crackers with cheese or apple and peanut butter.

...and adopt time-restricted eating

We’ve touched on three regular mealtimes, and the dangers of late-night snacking, but another simple approach when thinking about the relationship between time and your blood sugar is to restrict your mealtimest to a specific window in the day. Don’t panic - this is a lot easier than it sounds.  

First, a bit of science - we know that insulin sensitivity changes with your circadian rhythm, meaning it decreases throughout the day and into the night. And so any meal consumed at night is associated with higher glucose and insulin levels. To avoid this, you could limit your eating hours to earlier in the day, for example an nine hour window between 7am and 4pm, or 10am to 7pm. 

This is not only proven to improve your glucose levels, but can help with weight loss too. One study even found that time-restricted eating within a nine-hour window showed positive results, even when people were eating typical diets that weren’t restricted in any other way. [4] So it’s a win-win all round and yet another trick to helping manage your type 2 diabetes. 

[Healthy] carbs to start the day

Okay, so we know that skipping meals is a no-no, but breakfast is one that would be especially risky to miss. It wreaks havoc on blood sugar levels for the rest of the day, pushing them up until lunchtime, if not dinnertime, as one study found. [5] It could also impact mental clarity, with ducking out on breakfast causing lower cognitive function. [6] Mornings are already difficult enough - why make them any harder for yourself!?

Skipping meals to save calories sets the body up for fluctuations in insulin and glucose that leads to weight gain rather than weight loss

Kliewer et al, J Nutr Biochem

You may have heard the proverb: ‘Eat breakfast like a king, lunch like a prince, and dinner like a pauper.’ More than just a fridge magnet aphorism, this could be a genuinely beneficial approach for people with type 2 diabetes. One study found that an early breakfast that’s rich in starch, and therefore high in carbohydrates, improves glycaemic control and reduces the demand for insulin injections and medication. [7] Porridge or Weetabix with banana, sweet potato hash topped with eggs, or plain yoghurt with berries are all breakfasts of champions. 

However, if you’re experiencing the dawn phenomenon, which is when your blood sugar spikes in the morning, you might want to eat an early breakfast with lower carbohydrates and focus on higher protein foods in the evening, instead of a carb-heavy start to the day.  

In summary

So when you eat really does impact your blood sugar levels. However the small switches we’ve outlined above mean you can stay on top of these side effects. If you’re a grazer or free-ranger, they may be tricky to implement, so start small and aim to phase in these changes. Any repeat eaters are already on the straight and narrow. The most important thing is to find an approach that you can adopt in the long-term. Majorly ‘editing’ your eating schedule to fulfil the above can deliver quick results, but if you feel it’s going to disrupt the way you work, live, or that trip to Spain, choose set days you can adhere to. And there’s no point beating yourself up if you break with your routine - tomorrow, as they say, is another day. 


[1] Kliewer, K.L., Ke, J.Y., Lee, H.Y., et al. (2015). Short-term food restriction followed by controlled refeeding promotes gorging behavior, enhances fat deposition, and diminishes insulin sensitivity in mice. J Nutr Biochem 26(7): 721–728. Accessible here.

[2] Evert AB., Dennison M., Gardner CD., et al. (2019). Nutrition therapy for adults with diabetes or prediabetes: A consensus report. Diabetes Care 42(5); 731-754. Accessible here.

[3] Changing Timing, Frequency of Meals May Help With Diabetes. MedicineNet. Retrieved 5 May, 2021. Accessible here.

[4] Hutchison, A.T., Regmi, P., Manoogian, E.N., et al. (2019). Time‐Restricted Feeding Improves Glucose Tolerance in Men at Risk for Type 2 Diabetes: A Randomized Crossover Trial. Obesity 27: 724-732. Accessible here.

[5] Skipping Breakfast Bad Idea for Type 2 Diabetics. WebMD. Retrieved 5 May 5. Accessible here.

[6] Tang, Z., Zhang, N., Liu, A. et al. (2019). The effects of breakfast on short-term cognitive function among Chinese white-collar workers: protocol for a three-phase crossover study. BMC Pub Health 17(92). Accessible here.

[7] Jakubowicz, D., Landau, Z., Tsameret, S., et al. (2019). Reduction in Glycated Hemoglobin and Daily Insulin Dose Alongside Circadian Clock Upregulation in Patients With Type 2 Diabetes Consuming a Three-Meal Diet: A Randomized Clinical Trial. Diabetes Care 42 (12): 2171-2180. Accessible here.

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