Settling the internet's favorite weight loss debate. (and why this can be so confusing for people).
Is it calories in, calories out? Or is it hormones?
The internet loves to argue about weight loss....and when it comes to "hormones" or "calories" - both sides are actually right.
The confusing thing for people (this was me for YEARS) - is that both sides fail when their advice is followed without context.
Let me explain....
Keep reading for the full article!
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Click here for details. Respond to this email if you have questions about the program - we start on Monday the 26th of January.
To be honest I am not sure if I will offer this again - so join this time if this resonates for you.
The internet loves to frame weight loss as a fight between two camps: Calories in and calories out vs. hormones.
The truth is that both sides are actually pointing at real mechanisms, and both start to fall apart when their advice is followed without context in the wrong scenario.
Yes, fat loss requires an energy deficit. But (and this is where some confusion comes in) hormones and overall metabolic terrain determine how that deficit is experienced, how long it can be sustained, and whether the body adapts by burning fat or actively defending it.
Hormones like leptin, insulin, cortisol, thyroid hormone contribute heavily to regulating appetite, resting energy expenditure, spontaneous movement, and fuel partitioning. That’s why two people who are similar size & the same gender can eat the same calories and get very different outcomes over time.
So the point to understand hereis that: if you have dieted - restricted - and repeatedly signaled to your body that fuel is scarce, your metabolism adapts by lowering baseline energy expenditure.
A calorie deficit can still produce fat loss in this state - that part doesn’t disappear, but it becomes significantly harder to maintain.
Over time - Hunger signals intensify, energy output declines, recovery suffers, and the psychological and physiological cost of staying in a deficit increases. This is where many people burn out, feel unwell, or abandon the process entirely, not because the strategy is “wrong,” but because the system they’re applying it to has changed.
So my point is that while a calorie deficit remains the mechanism for fat loss, hormones and overall terrain determine how cooperative the system is. When those signals are supported - through light, timing, sleep, hydration and stress regulation - the same deficit becomes far more sustainable. That’s the difference between white-knuckling progress and working with physiology to get the best possible outcome!
Where light also changes the equation:
Light is overlooked - upstream signal that governs both sides of the equation.
Light is not just a circadian cue for sleep and wake cycles (although this is crucial for an efficient metabolism)...... It is also a primary environmental signal that programs metabolic efficiency at the cellular level.
What do I mean by that? The spectrum, timing, and intensity of light reaching the body - particularly infrared and red wavelengths - influence mitochondrial function, electron transport efficiency, and ultimately how much energy is available for work versus storage.
This is where the modern indoor lifestyle becomes a real metabolic problem.
Most people now spend the majority of their day indoors, behind glass. While visible light passes through windows, infrared light largely does not.
That distinctions is important, because infrared wavelengths are deeply involved in mitochondrial signaling and structure. The work of researchers like Glen Jeffery has shown that red and infrared light can directly improve mitochondrial function, ATP production, and cellular resilience, particularly in metabolically active tissues.
When that signal is chronically missing, mitochondrial efficiency declines, and the body shifts toward energy conservation rather than expenditure.
Large population datasets, including analyses emerging from UK Biobank (Dr. Jeffrey's lab), continue to show strong associations between outdoor light exposure, mitochondrial function, metabolic health, and all-cause mortality.
These relationships persist even when activity levels & food are controlled for, suggesting that light itself - not just movement or food- is playing a regulatory role. This aligns with growing evidence that circadian disruption, low daytime light exposure, and artificial lighting environments impair leptin sensitivity, thyroid signaling, glucose regulation, and resting metabolic rate.
In other words, when the brain perceives a low-energy environment - dim days, bright nights, limited (or zero) infrared exposure - it adapts accordingly: Appetite increases, and energy expenditure decreases (the body essentially thinks it's in the dark all day.
And back to my original point: The same calorie intake produces a very different biological response.
So yes, calories determine whether fat loss is theoretically possible. Hormones and terrain determine whether it is tolerable or sustainable. And light, particularly natural outdoor light across the full spectrum, influences both from the top down.
When any one of these layers is ignored, people tend to stall, burn out, or blame themselves for a system that was incomplete to begin with.
This is the framework behind the Bio-Individual Blueprint. It isn’t about picking a side in an online debate. It’s about understanding how your light environment, circadian timing, stress load, and metabolic signaling interact, so nutrition and energy balance actually work with your physiology to give you sustainable results.
Because of how individualized this work is, I only take a small number of people at a time. There are just four spots left in this round.
I had a fantastic time speaking with Nurse Practitioner - Heather Sandy - this week all about peptides (and how some of the stuff online is downright dangerous).
