Time to Be at Your Best: A Circadian Biologist’s Guide to Daily Health & Performance Optimization
Dr. Greg Potter
Greg Potter's PhD work at the University of Leeds on sleep, diet, and metabolic health was featured by the likes of the BBC World Service, the Washington Post, and Reuters. Greg has a BSc and an MSc in Exercise Physiology from Loughborough University, where he coached a sprinter to four gold medals at the European Championships. Greg has also worked with groups such as The United States Naval Special Warfare Command on health and performance optimisation. He is now Chief Scientific officer for a digital health startup.
Dr. Greg Potter explores how modern life disrupts our biological clocks, leading to health
It is not only what you do that matters, but when you do it is critical too.
Summary
- Synchronize the master clock by seeking high-intensity blue light during the day and minimizing light exposure at night to align biological rhythms with the environmental clock.
- Front-load calorie intake and practice time-restricted eating within a 6–12 hour window to optimize metabolic health, improve blood sugar regulation, and support weight loss.
- Perform strength and power exercises in the late afternoon when core body temperature is highest, but avoid heavy spinal loading and intense stress immediately after waking.
- Improve sleep by keeping bedrooms at 18°C and taking warm showers before bed; utilize short 10-minute naps during the afternoon "dip" to boost alertness and cognitive function.
- Maximize the effectiveness of medications and supplements by considering chronopharmacology, as the body's ability to metabolize substances varies significantly throughout the day.
Article
Time To Be At Your Best
A Circadian Biologist’s Guide To Daily Health And Performance Optimization
At Biohacker Summit 2019 Helsinki, held in Helsinki, Finland, on 1 and 2 November 2019, Dr. Greg Potter offered a brisk, evidence-led argument against one of modern life’s most quietly corrosive habits: living as though time did not matter.
His presentation, *Time to Be at Your Best: A Circadian Biologist’s Guide to Daily Health & Performance Optimization*, was not a sermon on productivity for its own sake. It was a case for biological humility. Human beings, Potter suggested, had not outgrown the ancient clocks that governed hunger, sleep, attention and repair. We had simply learned to ignore them, then mistaken the consequences for normal life.
Modern clock misalignment, he argued, was not merely an inconvenience of busy schedules or late-night screens. It was a driver of metabolic dysfunction, dulled cognition, poor sleep and declining resilience. The remedy was not a miracle supplement or a punishing protocol, but a more disciplined relationship with what chronobiologists call zeitgebers: the external time cues that reset the body each day.
The Three Clocks That Now Govern Modern Life
Potter, whose research at the University of Leeds examined sleep, diet and metabolic health, framed the issue in evolutionary terms. Once, he said, humans lived largely by two clocks: the environmental clock, defined by light and temperature, and the biological clock, developed to anticipate those changes. By day, people moved, ate, worked and gathered. By night, they rested, fasted and endured darkness.
Then came artificial light, all-hours eating, sedentary convenience and the rise of the social clock. Shift work became a brutal expression of that conflict. In a 24-hour society, large numbers of people now ate, laboured and remained alert at the very times their biology expected sleep.
The costs were not theoretical. Potter pointed to evidence linking circadian disruption with obesity, diabetes, coronary heart disease and stroke. Cognitive performance, too, suffered when the body’s timing systems were pushed out of sync. Jet lag, he noted, was simply the most familiar and democratised version of the same biological confusion.
Why Strong Time Cues Still Matter
“A characteristic of a healthy circadian system is consistently timed, high amplitude rhythms of wakefulness and rest,” Potter said.
That health, he argued, depended on robust time cues. Light was chief among them. The body’s master clock, housed in the brain, remained exquisitely sensitive to light and dark. Daytime bright light, especially in the blue spectrum, reinforced wakefulness and alignment. Night-time light did the opposite.
“The presence of strong time cues, which resynchronize our biological clocks each day, is important if you wish to feel and perform better,” he said.
Potter cited camping studies in which people exposed only to natural light for several days saw their sleep timing rapidly converge. Chronotype differences that seemed fixed in ordinary life narrowed substantially once modern lighting disappeared. It was a quietly radical point: many of the differences people thought of as personal identity might also be symptoms of weak environmental signals.
His prescription was simple in theory, harder in practice. Seek bright outdoor light early in the day. Minimise light exposure at night. Move during daylight. Fast during the biological night. The body, he suggested, still knew what to do when given a clear schedule.
Morning Light, Late Training, Earlier Meals
From that foundation, Potter moved into practical timing.
For exercise, he made a distinction that many fitness cultures tend to flatten. Not all movement belonged at all hours. Very strenuous exercise immediately after waking was ill-advised, he said, partly because the cardiovascular system was more reactive to stress in the morning and partly because spinal discs, rehydrated overnight, were more vulnerable to heavy loading.
If strength and power were the goal, late afternoon appeared to be the biological sweet spot. Core body temperature was higher then, nerve conduction faster, joint fluid less viscous and muscular energy systems more responsive. In plain language, the body was more prepared to perform.
For endurance training, he was more cautious, noting that ideal timing varied by individual. But for metabolic health, his warning was clearer. High-intensity training too early, especially in people with impaired blood sugar control, could be counterproductive. Late afternoon often looked more favourable.
His general rule was measured rather than dogmatic: exercise between one hour after waking and three hours before bed, where possible.
Eat Earlier, Eat Within A Window, Eat In The Right Order
If light set the master clock, food helped govern the clocks elsewhere in the body. Here Potter’s message was unmistakable. Regular feeding and fasting cycles strengthened circadian function. Erratic eating weakened it.
“Having regular, consistently timed cycles of feeding and fasting bolsters the function of your biological clocks,” he said.
He urged front-loading calories, especially carbohydrates, earlier in the day, when glucose tolerance was generally better. The body handled the same meal differently in the morning than in the evening. Calories consumed early tended to support better blood sugar control, improved metabolic health and, in some studies, greater weight loss.
Time-restricted eating also featured prominently. Potter described evidence suggesting that compressing food intake into a 6 to 12 hour window, particularly one skewed toward the earlier part of the day, could improve insulin sensitivity, lower oxidative stress and reduce blood pressure.
Then came one of the talk’s most practical interventions: nutrient sequencing.
Eat fibre and protein before carbohydrates, he advised. For people with poor blood sugar control, that simple change could sharply reduce post-meal glucose spikes. It was a small act with disproportionately large effects, and one of the more striking examples of how timing included not only when to eat, but in what order.
Sleep, Temperature And The Lost Art Of Winding Down
Potter’s account of sleep was equally grounded in physiology rather than mystique. The afternoon dip in alertness, he said, was not simply a consequence of lunch but part of the body’s daily architecture of wakefulness. Short naps, around 10 minutes, could deliver meaningful gains in alertness and cognitive function without the heavier grogginess of longer sleep.
Night-time, however, required a more deliberate descent.
A warm shower roughly an hour before bed could help the body cool itself by increasing heat loss through the extremities, thereby easing sleep onset. Bedrooms, he said, worked best at around 18C. Screens and work should stop at least an hour before bed. Rumination, a common thief of sleep at the start of the working week, could be blunted by writing a to-do list for the following day.
That recommendation carried a broader theme of the talk: biology did not merely respond to substances and stimuli. It responded to sequence, ritual and expectation.
Focus Earlier, Stress Smarter
Potter also extended circadian thinking to cognition and work. Attention generally worsened with time awake, he noted, which made a strong case for placing the most demanding and focused tasks early in the biological day. Deep work belonged to those earlier hours, before decision fatigue, distraction and sheer wakeful erosion took their toll.
He advised reducing task switching, muting the digital assault of phones and websites, and protecting periods of concentrated effort. Work stress itself, he suggested, was often better managed in the middle of the day than at its edges. Too early, and the cardiovascular response to stress was sharper. Too late, and stress tended to bleed into sleep.
Meditation, especially within two hours of waking, was another tool he recommended for resilience, though he acknowledged the difficulty many people had in turning it into habit.
When Medicines Work Depends On When You Take Them
One of the most quietly important sections of Potter’s presentation concerned chronopharmacology, the study of how medication effects vary according to biological time.
The body does not absorb, metabolise and excrete drugs uniformly across the day. Timing can alter efficacy, tolerability and even toxicity. Some medications for cancer and rheumatoid arthritis, Potter noted, have shown markedly improved performance when taken at the right time.
It was a reminder that modern medicine, for all its precision, often still treated time as an afterthought. Potter urged listeners to ask not only what they were taking, but when.
The Case For Measured Stress
Potter ended on a note that resisted the sterile fantasy of perfect routine. The body, he said, did not need a life emptied of challenge. It needed challenge in the right dose.
“Intermittent exposure to an appropriate dose of a stressful, sub-toxic stimulus can trigger biological defense mechanisms that result in the repair and enhancement of biological systems,” he said.
Fasting, cold exposure, sauna use and novel forms of exercise all belonged to this principle of hormesis, in which a manageable stressor provoked adaptation rather than harm.
“Occasional use of fasting, cold exposure, sauna use, and novel types of exercise is likely to be very beneficial for your health and performance,” he said.
It was an apt conclusion to a talk that consistently rejected excess. Potter did not propose an optimised life as one of relentless control. He proposed one of rhythmic intelligence: strong light in the morning, harder training later, food earlier, darkness at night, and occasional adversity to keep the organism honest.
In an era addicted to hacks, Dr. Greg Potter’s message at Biohacker Summit 2019 Helsinki was, in fact, more fundamental than that. The body had always been keeping time. Health, he suggested, began with learning to keep it too.
Part of Biohacker Summit 2019 Helsinki