Published research into differences between people in timing and in response to food · Read this before you follow yet another new nutrition plan
No new plan. No stricter rules. A free five-minute check that shows which signals in your own answers speak loudest.
"It works for them. Why not for me?"
You know your own version of that thought. Waking up tired after seven hours of sleep. Needing twenty minutes before you are capable of anything. That hour after lunch when your head goes foggy. Reading the same paragraph twice. Being too tired at half past seven in the evening for the thing you had been looking forward to. Legs like lead on a flat street. Cancelling on people and feeling bad about it.
I am Jesse van der Velde. Not a guru and not a doctor. I study and share what published research says about how a body ages. I have been testing that on myself and with the people I guide for more than fourteen years.
The thought I hear many people say is "am I doing it wrong".
Because there is published work on how far apart two healthy people can be on exactly the same day, and nobody has worked that into the advice you were given.
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Almost every nutrition plan you have read is written as if there is only one body.
Eat at these times. Sleep these hours. Move like this. That works, for the average of a group.
You are not the average of a group. You are one person, with one clock and one way of processing a meal.
So when it did not work, you drew the only conclusion the plan left you: you had not followed it well enough.
There are two published lines of research that say something else, and they are about differences between people rather than about willpower.
In 2006 Marc Wittmann, Jenny Dinich, Martha Merrow and Till Roenneberg published a study in Chronobiology International.¹
What was studied: how sleep quality and mental wellbeing relate to a person's chronotype, that is, the timing the internal clock of that person prefers, and to the gap between that timing and the timing their week demands.
How: 501 volunteers filled in the Munich ChronoType Questionnaire, plus questionnaires on sleep quality, how they felt at that moment, how they had felt over the past week, and their use of stimulants. This is questionnaire research, so what comes out of it are associations and not causes.
The findings: people differ strongly in the timing their body prefers, from extreme early types to extreme late types, with most people somewhere in between. For the greater part of the population, work and school schedules cut straight across that preference. Late types show the biggest difference between when they sleep on workdays and on free days, so on workdays they build up a sleep debt that they then catch up on free days. That gap between social time and biological time is what the authors call social jetlag.
Read that again. Two people with the same office hours are not running the same week, because their internal timing is not the same.
Now the afternoon, on its own.
In 2005 Timothy Monk published a review in Clinics in Sports Medicine.²
What was studied: whether that drop in performance in the middle of the afternoon is caused by lunch.
How: a review of laboratory work, including studies in which that dip shows up in people who had eaten no lunch at all and did not know what time it was.
The findings: the dip is real, it goes together with a rise in sleep pressure at that time of day, and it also comes without lunch and without anyone knowing the time. It has roots in human biology. A lunch high in carbohydrates does make it worse, and it may be more common in extreme morning types.
Note the caveat the author puts in the very first sentence, because that is the honest part: this holds for some measures of performance and for some people. That is what this whole page is about.
So part of your four o'clock sits on a clock. And which clock that is, and how hard it hits, is not the same for you as it is for them.
Does this sound familiar? Take the free check now.
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46,898 meals. In 2015, David Zeevi, Tal Korem, Niv Zmora and colleagues published in Cell. They followed blood sugar continuously in 800 people for a week and measured the response to 46,898 meals.³
Wide variation, on the same meal. That was the finding. Blood sugar responses to identical meals differed strongly from person to person, and so the authors wrote that universal nutrition advice can be of limited use. They then built an algorithm out of blood values, eating habits, body measurements, physical activity and gut bacteria, showed that it predicted a person's response to real meals, validated that in a separate cohort of 100 people, and put a blinded randomised dietary intervention on top of it, which significantly lowered the responses after the meal.³
Three steps, in that order: measure, predict, and then test the prediction. That is what makes this more than an observation.
508 kilocalories a day. In 2019, Kevin Hall and colleagues published a randomised study in Cell Metabolism, in people who were admitted to a clinic. 20 adults with a stable weight, on average 31 years old, ate either ultra-processed or unprocessed meals for two weeks, and then the other kind for two weeks. The meals were matched on calories offered, energy density, macronutrients, sugar, sodium and fibre, and the participants could decide for themselves how much they ate. In the weeks with ultra-processed meals they ate 508 kilocalories a day more (p is 0.0001) and gained 0.9 kilos; in the weeks with unprocessed meals they lost 0.9 kilos.⁴
Nobody in that study decided to eat more. The difference was in what was put on the table in front of them.
You know your own version of this. Mine is a colleague who was sharp at half past seven in the morning and kindly told me they simply went to bed earlier.
I tried it for a month. I lay awake and still got up tired.
For years I read that as a discipline problem. It was a timing problem, and that timing was not the same as theirs.
A judgement about your character gets you nowhere. Nothing constructive comes out of it. You cannot try harder to be a different person.
The difference between your week and theirs has been measured in published research. Yours has not.
1. Going to bed an hour earlier on a work night.
Whether you do that is of course up to you, and for some people it is exactly right.
But be clear about what it does and does not do. It gives you more time in bed. It does nothing about the gap between your internal timing and the timing your week demands, and in that study it is the late types who show the biggest difference between working days and free days.¹
2. Catching up at the weekend.
People already do that without making a decision about it. In that same research, late types catch up on free days on the sleep debt they build up on workdays.¹
What it does: give back part of the sleep. What it does not do: change anything about the difference that built that debt, because that is simply waiting again on Monday.
3. Blaming lunch.
The review says the afternoon dip also shows up in people who had eaten no lunch and did not know what time it was.² So lunch is not the whole story. A lunch high in carbohydrates does make it worse, and that is worth knowing, and it is a smaller finding than the one people carry around with them.
4. Taking over the plan that worked for someone else.
This is what the glucose research speaks to directly. 800 people, 46,898 meals, and the responses to identical meals varied widely from person to person.³ The authors' own conclusion: universal dietary advice may be of limited use.
You were not undisciplined. You were following a plan built for the average of a group whose average you are not.
Four moves, one shared problem: none of them starts with what is actually going on with you.
The advice failed here, and it was the sensible sounding kind. You did nothing wrong. It can be different.
This is the heart of it. If two healthy people differ this much from each other on the same day, then "what should a person do" is no longer the useful question.
The question becomes: what does my own week actually report?
When the tiredness comes. What it costs you. Whether it sits in the morning, after lunch, or at half past seven in the evening. Whether it lands in your head or in your legs.
That is what the research made available. Wittmann and colleagues showed that the difference between biological and social timing is common and measurable.¹ Zeevi and colleagues showed that a personal analysis beats a general rule, and then tested that in a blinded study.³ And Hall and colleagues showed that what is put in front of you shifts your intake by 508 kilocalories a day without you deciding anything.⁴
What there was not: a way to lay your own week alongside it.
On one condition. That analysis has to be about you: your energy through the day, your dips, your own answers, question by question, set beside what published research describes. A general list of energy tips does not tell you which signals in your week are the hard ones.
BioProfile has built that first step. A scientifically validated questionnaire, five minutes, free and with no account.
You answer questions about your energy through the day and about your daily life. After that you see which signals in your profile speak loudest, and what the research says about them. Not a medical examination. An analysis of your own answers. You use the outcome yourself, or you put it on the table with your doctor or your coach.
Then the daily side. What I put into it myself every morning is a glass: Green Juice, a plant-based all-in-one daily drink mix with more than 44 ingredients, including vitamins, minerals, herbs, grasses, fruit, vegetables, algae, probiotics and digestive enzymes. The B vitamins in it and minerals such as chromium and potassium contribute to a normal energy-yielding metabolism and to the reduction of tiredness and fatigue through the day. One glass, every day, as a steady base.
And to say it plainly: this is a daily nutrition baseline. You still read your own timing yourself. That is what those five minutes are for.
You do the free check. Five minutes, no account, and there is nothing to buy.
Even if you do nothing with it, you have traded "so I am doing it wrong" for an analysis of your own answers. That trade is worth five minutes.
And the next time someone tells you what works for them, you will know what your own week reports.
Do it while this page is still open. Tomorrow runs on your clock either way.
Our scientifically validated questionnaire gives you answers
The scan is not a medical examination. It is an analysis of your own answers. If complaints persist, consult your doctor.
