He literally rolls into my office every three months, shoes still clipped to his carbon-fiber lifestyle. Lycra damp, Apple Watch buzzing, resting heart rate of 42. He is fit, smart, and tightly wound.
“Doc,” he begins, eyes wide, “I read that morning workouts burn more fat and lower clotting factors. Should I move my rides earlier? Or maybe late evening is better for heart rate variability?”
This is a man who, when he is not on his bike, is in an internet rabbit hole about the next marginal gain. He already trains more in a week than most of my patients manage in a year. Yet here he is, anxious that his 6 p.m. spin class might be shortening his life.
Here is the truth I tell him, and now you: It does not matter.
The science (such as it is)
Yes, there are studies. The UK Biobank analysis of 90,000 people found morning exercisers had slightly lower rates of coronary events. Another trial suggested evening workouts improved lipid metabolism and resting heart rate overnight. Afternoon training may line up with circadian peaks in lung function and muscle strength.
The problem? These effects are modest, inconsistent, and likely irrelevant to the average person who can barely squeeze in a thirty-minute walk three times a week. They are statistically significant in the way that makes careers in exercise physiology, not in the way that saves your patients’ lives.
The heart does not own a clock.
Your myocardium does not know if the sun is rising or setting. It knows shear stress, stroke volume, and whether the endothelium is being challenged. It knows if you are moving most days, for years.
Medicine has a bad habit of fetishizing precision while ignoring the obvious. We argue about LDL subfractions while our patients keep smoking. We debate kale versus quinoa while they mainline soda. And now, we are letting them believe there is a “perfect” hour to sweat.
The real prescription
The best time to exercise is the time you will not cancel. Early bird? Run at dawn. Night owl? Gym after dinner. Parent of toddlers? Congratulations. Your window is whenever Paw Patrol buys you twenty-seven minutes of peace.
Consistency trumps clock time. Habits beat hacks.
Why this matters for doctors
Every time we indulge the “optimal timing” debate, we feed the anxious, over-quantified patients who think health is unlocked by gaming circadian biology. Meanwhile, the rest of our panel is sedentary and waiting for a stent.
Our job is not to manufacture new anxieties. It is to simplify. To remind people that movement is medicine, and that the dose, not the timestamp, is what counts.
My irreverent takeaway
So here is what I tell my patient:
“Ride when you damn well please. You are already doing the hard part. If you want a real marginal gain, stop worrying about when to exercise and start worrying about whether you will keep exercising when you are 70.”
If he follows that advice, he will live longer. And I will spend less time debunking PubMed abstracts disguised as wellness hacks.
Bottom line: The best time to exercise for heart health is the time you will actually do it again tomorrow. Everything else is noise.
Larry Kaskel is an internist and “lipidologist in recovery” who has been practicing medicine for more than thirty-five years. He operates a concierge practice in the Chicago area and serves on the teaching faculty at the Northwestern University Feinberg School of Medicine. In addition, he is affiliated with Northwestern Lake Forest Hospital.
Before podcasts entered mainstream culture, Dr. Kaskel hosted Lipid Luminations on ReachMD, where he produced a library of more than four hundred programs featuring leading voices in cardiology, lipidology, and preventive medicine.
He is the author of Dr. Kaskel’s Living in Wellness, Volume One: Let Food Be Thy Medicine, works that combine evidence-based medical practice with accessible strategies for improving healthspan. His current projects focus on reevaluating the cholesterol hypothesis and investigating the infectious origins of atherosclerosis. More information is available at larrykaskel.com.
