Following on from my post about carbs – it kind of leads into the bigger picture of energy balance, calories, and how we tackle goals like fat loss or building muscle. It opens up the bigger picture of energy balance – the calories coming in versus the calories going out – and how it relates to our gym goals, food choices, and overall health.
Our Total Daily Energy Expenditure (TEE) – the total calories burned in a 24-hour period – is made up of a few key components.
The biggest slice of the pie for most people (often 60-75% of TEE) is the Basal Metabolic Rate (BMR). I used to tell people this is your body's "idling speed" – the energy burned just to keep vital functions going if you were completely at rest: breathing, blood circulation, maintaining body temperature, brain activity, cell repair etc...
There's quite a lot that influences your BMR and it's not the same for everyone. The list isn't exhaustive but there's a few here:
- Body Size (Weight & Height): Larger bodies generally require more energy to maintain.
- Body Composition: This is super relevant for us – muscle tissue is significantly more metabolically active at rest than fat tissue.This means building and maintaining muscle mass through resistance training directly increases your BMR over time!
- Age:BMR typically declines slowly with age, partly linked to changes in muscle mass.
- Sex: On average, men tend to have higher BMRs, largely due to differences in average size and body composition.
- Genetics & Hormones (like thyroid function) also play a part.
- Then you have the Thermic Effect of Food (TEF): The calories burned digesting and absorbing the food you eat (protein has the highest TEF)
- Activity Energy Expenditure (AEE): This covers everything from planned exercise sessions (like lifting or cardio) to general daily movement, walking around, fidgeting etc. (often called NEAT - Non-Exercise Activity Thermogenesis).
So, the challenge often is that modern diets (especially now with the prevalence of UPF) can drive excess calorie intake, while our adaptive calories burned (Constrained TEE) makes it hard to just burn off that excess through activity alone. This highlights why focusing on both dietary quality (minimising UPFs, nutrient variety) and overall quantity (calories aligned with goals) is key.
Diving into the point about our bodies potentially constraining energy expenditure, as it challenges a lot of common assumptions. The traditional view was pretty simple: your baseline metabolism (BMR) plus digestion costs plus activity calories equals your total daily burn. Exercise more, burn more overall – simple addition.
However, research, particularly groundbreaking work by anthropologist Professor Herman Pontzer studying groups like the Hadza hunter-gatherers in Tanzania, paints a more complex picture. The Hadza live incredibly physically demanding lives, far more active than typical Westerners. Yet, when Pontzer and his team used gold-standard methods (doubly labelled water) to measure their TEE and crucially, adjusted the figures for body size and composition, they found the Hadza's average daily calorie burn was remarkably similar to that of people living much more sedentary lives in the US and Europe.
This wasn't a one-off; similar patterns have been seen in other populations too. This led Pontzer to propose the "Constrained Total Energy Expenditure" model. The core idea is that over evolutionary time, our bodies have developed ways to keep our total daily energy budget within a relatively tight range, regardless of huge variations in physical activity.
When energy spent on activity goes way up, the body seems to adapt and compensate by reducing the energy allocated to other, less immediately vital physiological processes. The savings have to come from somewhere – the thinking is it could be subtle down-regulations in areas like inflammation levels, immune system responses, stress hormone production, cellular repair and turnover, perhaps even reproductive functions over the long term.
Essentially, the body cleverly rebalances its energy budget. The major takeaway is that physical activity, while burning calories itself, doesn't necessarily increase your total 24-hour energy expenditure in a straightforward, additive way, especially at higher or sustained activity levels. This provides a strong physiological basis for why creating a substantial calorie deficit purely through exercise is so challenging for weight loss – the body fights back by conserving energy elsewhere, making dietary management the more potent lever for altering overall energy balance.
There is a trade off (in extreme cases) such as reproductive functions, immune function and over training syndrome, tissue repair and injury plus potentially other illnesses but these potential negative trade-offs seem most relevant under conditions of extreme and prolonged energy demands, often coupled with insufficient calorie intake or inadequate recovery. Overall the vast majority of people engaging in regular moderate-to-vigorous exercise as part of a balanced lifestyle, the profound health
benefits (including improved immune function and reduced chronic disease risk) are the dominant outcome. The body is generally well-adapted to handle reasonable levels of activity.
What about those needing loads of calories (e.g., 4000+)? (ie. people like me, I'm on just over 4k cals a day on average). Quite simply it's because of:
- Having a higher BMR: larger body size or more muscle mass needing more cals.
- Higher AEE: Fuelling high intensity levels of activity (1 martial arts session burns at least 800 cals for me and I do at least 3 a week, plus lifting 2-3x a week) requires massive amounts of energy, resulting in a high TEE even with some metabolic compensation.
- Specific Goals: Actively building or maintaining muscle requires a calorie surplus above the TEE.
Highly trained individual's high intake reflects their specific energy demands (a high TEE) or goals (a surplus), not a contradiction of the principles.
Managing weight and reaching gym goals involves understanding energy balance (TEE = BMR + TEF + AEE). Building muscle boosts our BMR. Prioritising nutrient-dense whole foods over UPFs helps manage the calorie intake side effectively. Consistent exercise is non-negotiable for health and body composition, even if TEE adapts. Tailoring overall calorie intake (deficit, maintenance, surplus) to your specific goals, body, and activity level, while respecting our body's adaptive nature, is the path forward.
All that is more important than worrying about carbs alone.
This is a bit of a hobby of mine and something I've been reading up on for nearly 2 decades now! 
This is not sensationalism unfortunately, it's been proven 
But health inequality benefits so many people (and politicians) but that's another rant for another day!