The Link Between Food, Energy and How Grateful You Feel

By Matt Hughes · 2026-06-04 · 9 min read

I started noticing, in my own journal, that the days I felt least grateful were almost never the days I thought they were. They were the days I'd eaten badly, slept poorly, and run on caffeine. The pattern was a bit embarrassing once I saw it.

The link between food, energy and how grateful you feel is, it turns out, more direct than I'd ever quite let myself believe. I'd been journalling most evenings for about three months when I started noticing something a bit embarrassing in the entries. The days I'd written things like "felt flat", "couldn't summon much", "nothing came to mind tonight" weren't, on the whole, the days something bad had happened. They were the days I'd eaten a rubbish lunch at my desk, skipped breakfast, drunk four coffees, and then wondered, at half nine at night, why I felt morally incapable of finding anything to be grateful for.

This isn't a wellness post. I'm not about to tell you to drink celery juice or eliminate seed oils or any of the rest of it. I'm a slightly tired UK-based consultant who eats too much toast and drinks too much coffee, and the thing I want to write about is the small, specific, slightly annoying way that what you eat and how much energy you have appears to set a ceiling on how grateful you can feel — and how I only really worked this out because I happened to be writing it down at the same time.

Why does a bad lunch ruin your evening gratitude?

I'll start with the most repeatable one, because it's the one I've now seen in my own journal probably forty times. If I eat a sandwich and crisps and a Coke at twelve, somewhere around three I'll have what I used to call "a flat afternoon" and now call, with slightly more accuracy, "a blood sugar afternoon". By six I'm a bit irritable. By nine, when I sit down to write, the entries are noticeably worse. Not dramatically worse. Just slightly more grumbling, slightly less specific, slightly less likely to land on anything that actually pleased me.

What I didn't expect was how consistent the pattern would be once I started flagging it. I'm not a careful eater. I don't track macros. But I started, in a half-arsed way, jotting down what I'd had for lunch alongside the evening entry — just a line at the bottom. Sandwich. Salad. Whatever. After a month of this I could see, clearly, that the salad-and-something-warm days produced different writing than the meal-deal days. Not because salads are virtuous and meal deals are sinful. Because one keeps your blood sugar reasonably stable for the afternoon and the other puts you on a small rollercoaster you won't necessarily notice until it's affected your mood.

If I'm honest, this annoyed me. I quite liked the idea that gratitude was a sort of pure, top-down practice — something you trained, like a muscle, regardless of circumstance. The data in my own notebook said otherwise. The notebook said gratitude was, to a depressingly material degree, downstream of glucose.

Is it really the food, or is it the tiredness?

This was the obvious counter-argument, and the one I rolled out for a few weeks before I'd really had a proper look at the entries. Maybe the bad-food days were also the busy days, the stressful days, the late-night days, and the food was a symptom rather than a cause.

That's partly true. They overlap. But not as much as I'd assumed. There were plenty of busy, stressful days where I'd happened to eat properly — a leftover dinner reheated for lunch, a real breakfast — and those days, on the whole, produced more generous entries than the lazy-week days where I'd grazed on toast and biscuits in a quiet house. Stress matters. But food matters independently. It's its own variable.

What I've found, and what surprised me, is that energy is the thing the food is really controlling. The food isn't directly making me ungrateful. It's making me tired, in a low-grade, all-day way I'd stopped noticing because it was so familiar. And tired, it turns out, is hard ground for gratitude to grow in. Tired makes everything feel slightly more grey, slightly more deserved, slightly less worth commenting on. You don't write "I'm grateful for the sunshine through the kitchen window" when you're tired. You write "fine" and close the notebook.

What does caffeine have to do with any of this?

More than I'd like, is the honest answer. I drink coffee. I'm not giving it up. But the pattern in my entries on three-coffee days versus one-coffee days is real enough that I now think about it before I make the fourth one.

Caffeine, for me at least, does a strange thing to the gratitude window. The morning entries on heavy-coffee days are often quite buzzy and slightly performative — lots of "amazing" and "incredible" and not much actual specificity. The evening entries on the same days are noticeably worse. Flatter, more terse, more "can't really think of anything tonight". It's as if the caffeine borrows the gratitude from the evening and spends it in the morning, with interest.

This is a small thing. It is, in another sense, a quite big thing. If you're trying to journal at night — which most people are, because that's when there's time — and you're drinking a lot of coffee in the day, you may be quietly sabotaging the practice you're trying to build, and you'd have no way of knowing because the cause and the effect are eight hours apart.

Why do we forget the food when we look at our mood?

Because food is dull. Because mood feels like it ought to be about life events and inner work and meaningful things, and "I had a soggy sandwich and now I'm in a bad mood" feels reductive and slightly insulting to the seriousness of the inner life. I felt this myself when the pattern first started showing up in my journal. I wanted my bad days to be about something worthier than a meal deal.

But the brain doesn't seem to care what we'd prefer to be true. The brain runs on glucose and water and sleep and a few other unromantic inputs, and when those are off, it does its job badly. Gratitude is a job the brain does. It's a particular kind of attention — a noticing-the-good, a holding-it-still-long-enough-to-name-it. It costs energy. It costs more energy than most people realise. And when the brain is short on energy, it triages. Naming the good is one of the first things to go, because it's not necessary for survival. Surviving is necessary for survival. Noticing the sunshine is a luxury, and a tired brain will skip it without telling you.

This is the bit I think actually matters. We tend to treat gratitude as a mental skill we either have or don't, a habit we either keep or lose. It's both of those things, but it's also a biological function with biological prerequisites. You can't think your way out of a hypoglycaemic afternoon. You have to eat something.

What I changed once I noticed the pattern

Not very much, if I'm honest, because the version of me writing this blog is not capable of overhauling his diet on the strength of a journalling insight. But the small changes I have made have produced disproportionate results, and I think they're worth sharing because they're realistic.

The first one was a real breakfast. Not a green smoothie. Eggs on toast, most days. Twenty minutes, properly sat down. The afternoon flat-spot got noticeably smaller, and the evening entries got noticeably warmer, within about a fortnight. I'm not sure which part of that did the work — probably the protein, probably the not-skipping, probably the slowing down. But the entries are the evidence.

The second was capping coffee at two cups before noon, with the third only if I really needed it. This was harder than it sounds. Three cups is my natural setting. But on the days I've held to two, the evening writing is better, full stop. More specific, less grumbling, longer entries.

The third was something my partner said, which was that I should drink a glass of water before deciding I was in a bad mood. I rolled my eyes at the time. It's worked annoyingly often.

None of these are revolutionary. They wouldn't make a wellness influencer rich. But they're examples of the kind of thing you only really act on once you've seen the pattern in your own writing — because the pattern is what makes the boring advice feel personally relevant, instead of generic. "Drink water and eat breakfast" sounds like the back of a cereal box. "I can see, in my own notebook, that the days I forgot breakfast produced worse gratitude entries by a measurable margin" is a different kind of evidence, and it's the kind that actually changes behaviour.

Does this mean gratitude is just about blood sugar?

No. I want to be careful here, because I'm not making the daft claim that gratitude is reducible to glucose. There are days I've eaten well, slept well, and still felt ungenerous, and there are days I've eaten badly and still landed somewhere warm by the end of the entry. Mood is multi-causal. Food is one input among several, alongside sleep, exercise, stress, weather, what's going on with the people you love, and whether the boiler is working.

But food is the input I'd been most under-counting, and I suspect I'm not alone in that. We pay quite a lot of attention to sleep these days. We pay a fair bit to exercise. Food, we mostly pay attention to in terms of weight or guilt or ethical concerns, not in terms of the hour-by-hour effect it's having on our capacity to feel good things. That gap is, I think, where the link between food, energy and gratitude has been hiding in plain sight.

What you could try tonight

If you're already journalling, the experiment costs you nothing. Add one line at the bottom of each entry for the next two weeks: what you had for lunch, and roughly how much caffeine you drank. Don't try to be virtuous about it. Just record. At the end of the fortnight, read the entries back and see if you can spot the pattern. You might not have one. I think you probably will.

If you're not journalling, the experiment is a bit bigger but still small. Three prompts, five minutes, every evening. What went well today. What's on my mind. One thing I'm grateful for. Add a single line at the end with what you ate at lunch. That's it. After a month you'll have enough data to see what's true for you, rather than what's true for me or for a study or for the back of the cereal box.

What I'd say, gently, is that the practice of gratitude turns out to be more physical than I expected. Not less spiritual, not less meaningful, not less worth doing. Just more rooted in the body than the version of it I grew up with. The good news is that gives you more handles. If your gratitude practice has stalled, the answer might not be a better prompt or a deeper insight. It might be lunch.