Not All Calories Are Equal: The Real Science of Weight, Food & Energy After 40
- Mahendra Rathod
- 2 hours ago
- 10 min read
“Understanding the body isn’t rocket science, it’s more complicated than this.” - Author: Unknown
Disclaimer: These are my personal experiences and learnings from science and reading. Please don’t take this as medical advice. If you have health concerns, talk to a doctor. I’m sharing what worked for me - and why.
A Few Years and a Few Lessons Later
When I wrote my earlier post, 12 Must-Read Books to Transform Your Health Life, I was 43. Curious, a bit experimental, and trying to figure out how my body actually worked.
Now at 46, I can say something I couldn’t say back then, that I feel fitter, stronger, and calmer than I did in my 30s.
I swim three times a week - about 1 to 1.5 km in 90 minutes - and go to the gym two to three times a week. I’m no Greek god (gin deserves some blame), but I’ve never felt better. My metabolism is sharper, recovery quicker, and mental focus steadier.
My lunch looks roughly like this:
A full plate of salad - cucumber, beetroot, tomato.
A solid serving of dal or tofu for protein.
One jowar roti for carbs.
Rice rarely, sweets occasionally.
And yes, 30 grams of protein powder right after workouts.
These habits didn’t happen overnight - they came from curiosity and failure in equal measure. What I’ve learned along the way is simple:
Calories are not just numbers, they’re stories your body interprets differently.
And trust me, not all calories are equal.
1. What Exactly Is a Calorie?
A calorie is just a unit of energy — nothing mystical. But the slogan “a calorie is a calorie” is the nutritional equivalent of saying all books are the same because they have pages. Technically correct, practically ridiculous. Your body reacts very differently to 100 calories of tofu, 100 calories of jalebi, and 100 calories of bourbon. Chemistry, hormones, digestion speed — they all rewrite the math before those calories ever meet your waistline.
Calories come in different forms and packages:
Nutrient | Calories per gram | Role |
Protein | 4 | Builds and repairs tissue |
Carbohydrate | 4 | Quick energy source |
Fat | 9 | Long-term energy and hormone support |
Alcohol | 7 | Energy that your liver babysits while everything else waits. |
The first three are nutrients. The fourth convinces you to make a call to your ex at 1am which you regret later!
A calorie doesn’t just add energy. It changes how your body behaves - how hungry you feel, how hormones react, how your metabolism fires. That’s why 200 calories of almonds don’t act like 200 calories of cola.
2. The Famous Equation That Lies by Omission
We’ve all heard it:
Calories In – Calories Out = Weight Change.
Sounds simple, like an Excel formula. Eat less, move more, lose weight. Done.
Except the human body is not Excel. It’s a negotiation, one that constantly adjusts to protect you.
When you eat less, your body lowers its energy expenditure. Your metabolism slows down, hormones shift, and your body quietly reduces unnecessary activity.
As Dr. Jason Fung writes in The Obesity Code, (Amazon Link)
“Your body isn’t trying to sabotage you. It’s trying to save you.”
When calories drop drastically, your body interprets it as famine, not fitness. It defends itself by burning fewer calories, increasing hunger, and conserving fat.
So yes, cutting calories works for a while. But then your body recalibrates, and the numbers stop adding up.
That’s when most diets “fail". In truth, the diet didn’t fail, the math did.
3. When the Body Fights Back
I’ve experienced this personally. When I first tried calorie restriction in my 30s, the weight dropped fast. Then came the plateau. Then fatigue. Then hunger that felt primal.
I wasn’t weak; I was simply human.
The body’s natural response to restriction includes:
Slower resting metabolism
Muscle breakdown for quick fuel
Elevated hunger hormones (ghrelin)
Reduced satiety hormones (leptin)
Heightened inflammation if recovery and sleep are poor
Dr. Robert Lustig in Metabolical (Amazon Link) calls this “the famine defense”. The body doesn’t know you’re dieting for a holiday. It thinks you’re trying to survive an ice age.
The rebound weight gain that follows? That’s not your lack of discipline. It’s your biology resetting its safety buffer a little higher “just in case".
And that’s how most fad diets fail: they make you lighter for a moment, then heavier for good.
4. A Calorie Is Not a Calorie. Here’s Why
This is where the story gets interesting. Calories behave differently depending on four key factors: timing, source, age, and metabolism.
a) Timing Matters
Your body runs on circadian rhythm — your internal clock. It’s more metabolically efficient in the morning and early afternoon. Late-night eating often leads to higher fat storage because insulin sensitivity drops after sunset.
I’ve noticed this myself. A hearty lunch fuels me all day; a late dinner slows me down and bloats me the next morning.
“Eat with the sun, not against it.”
It’s not about intermittent fasting trends; it’s about respecting your biology’s timing.
b) Source Matters
All calories don’t burn alike. Here’s how they differ:
Protein burns hot. Your body uses up to 30% of protein calories just to digest it (the thermic effect). It also boosts satiety and preserves muscle.
Fats and carbs digest easier, using only 5–10% of their calories for processing.
Whole foods (dal, nuts, vegetables, salad) deliver fiber and micronutrients that slow digestion and keep blood sugar stable.
Processed foods are stripped of those brakes — they spike and crash your energy.
Alcohol gives 7 calories per gram but disrupts sleep, hormones, and fat metabolism.
As Dr. Michael Greger writes in How Not to Diet (Amazon Link),
“Processed calories are the most efficient way to grow fat and stay hungry.”
The source of a calorie decides its destiny.
c) Age Matters
Once you cross 40, the rules change. Your metabolism slows 2–3 percent every decade. Muscle mass begins to decline unless you deliberately maintain it. That means you could be eating the same food you did ten years ago and still gaining weight.
This isn’t punishment. It’s a call to action. Resistance training and protein intake can reverse most of that decline. When you build muscle, you build your metabolism.
“Muscle is the only anti-aging organ you can build.” — Peter Attia, Outlive
Muscle doesn’t just help you look toned; it’s your best insurance against slow aging, injury, and metabolic disease.
d) Metabolism & Microbiome Matter
Metabolism is not a fixed number; it’s an ecosystem. Two people can eat the same meal, yet one burns it off easily while the other stores it. Why?
Differences in gut bacteria (the microbiome).
Variations in sleep quality and stress levels.
Hormonal factors and genetics.
Dr. Herman Pontzer explains in Burn (Amazon Link) that the body constantly adapts to inputs like activity, stress, and even climate. Your gut bacteria determine how much energy you absorb, how well you regulate blood sugar, and even how hungry you feel later.
Treat your microbiome like a quiet business partner. Feed it real food and it’ll reward you. Feed it junk, and it’ll start hoarding resources for a crisis that never comes.
5. Outsmarting the Calorie Game
Now that we know calories are complex, let’s focus on what actually works. Especially after 40, when recovery is slower and discipline has to be smarter.
1. Exercise : Train, Don’t Just Move
Exercise is your body’s way of saying, “We’re safe; we can burn fuel". When you train regularly: lift weights, swim, run, cycle, your body understands that it needs muscle, not fat, for survival.
Muscle tissue is metabolically expensive. It burns energy even while you sleep. Losing muscle with age is like closing your body’s most productive factory.
“Muscle isn’t vanity; it’s vitality.” — Peter Attia, Outlive
In short: train like your future depends on it. Because biologically, it does. Motion is nice, but muscle is the only insurance policy that actually pays out.
2. Sleep : The Hidden Metabolic Tool
Sleep is not rest; it’s repair. During deep sleep your body rebuilds tissue, balances hormones, and resets insulin sensitivity. Miss that window and your hunger hormones go haywire.
One bad night can increase appetite by 300–500 calories the next day. It’s not lack of willpower; it’s chemistry.
I’ve found that a 20-minute nap in the afternoon often gives me the clarity and calm that coffee promises but rarely delivers. The days I sleep well are the days I crave less and perform better, whether in the gym or at work.
3. Food & The Order of Eating
I’ve experimented with this sequence for years, and it’s the simplest upgrade most people can make: Fibre → Protein → Carbs → Sweet (if any).
Example: Start with a salad or veggies, then have dal or tofu (protein), then eat your carbs, jowar roti or brown rice, and if you really want, finish with a small dessert.
This order slows digestion, flattens glucose spikes, and keeps you full longer. It’s not magic; it’s biology.
As Dr. Robert Lustig writes in Metabolical, “Sequence is the unsung hero of metabolism.”
And while we’re talking about sequence: yes, 1 gram of alcohol gives you 7 calories. They’re like guests who show up late, talk loudly, and leave the place messier than they found it. So place them wherever you want, but they will screw up.
4. Hydration : The Quiet Player
Even mild dehydration can reduce metabolic efficiency. It confuses your hunger signals and makes digestion sluggish. I start my day with 300–400 ml of warm water, it wakes me up faster than caffeine. Through the day, I keep sipping rather than gulping. Warm, cold, or room temperature - it doesn’t matter as much as being consistent.
Hydration is the cheapest health insurance you’ll ever buy.
5. Stress & Inflammation : The Invisible Enemies
Stress is the tax your mind charges your body. Chronic stress keeps cortisol levels high, which raises blood sugar, increases abdominal fat, and breaks down muscle. Inflammation joins in, quietly damaging tissues and aging you from the inside out.
Dr. David Sinclair in Lifespan notes, “The body doesn’t age evenly. It ages in bursts, especially under chronic stress.”
To manage mine, I rely on short mindfulness breaks, occasional swims, and laughter. Choose your antidote: meditation, walks, music, whatever resets you. The best workout plan won’t help if you’re constantly inflamed.
6. Get Professional Help (or Outsource Discipline)
If discipline doesn’t come naturally, outsource it. A good trainer, mentor, or coach can push you when motivation fails. They keep your form safe and your effort consistent.
It’s not weakness to ask for help. It’s efficiency. You can’t delegate push-ups, but you can delegate discipline.
6. Quick Hacks That Actually Work
I love small changes that give big returns. These are science-backed, easy to remember, and they add up fast:
Food labels lie. Packaged food calorie counts can be off by up to 20 percent.
Protein wins. Digesting it burns up to 30 percent of its own energy.
Sleep more, eat less. One poor night can add 300–500 calories the next day.
Walk after meals. Ten minutes of movement smooths sugar spikes dramatically.
Drink cold water. Your body burns a few extra calories warming it up; small, but free.
Each of these is simple, almost boring. But do them consistently and they’ll do more for you than the latest diet trend.
7. The Books That Changed My Understanding
If you want to go deeper, here are eight books that reshaped how I think about calories, health, and longevity.
Why We Get Fat – Gary Taubes (Get a copy)
Explains why insulin and hormones, not discipline, drive weight gain and loss.
Metabolical – Robert Lustig (Get a copy)
A brilliant breakdown of how processed food damages metabolism and health.
The Obesity Code – Jason Fung (Get a copy)
The science of fasting, hormones, and long-term fat loss (without the calorie obsession).
How Not to Diet – Michael Greger (Get a copy)
Turns thousands of studies into actionable advice on what really works.
Outlive – Peter Attia (Get a copy)
A guide to living stronger for longer by focusing on strength, muscle, and metabolic health.
Lifespan – David Sinclair (Get a copy)
Explains why we age, and how we can slow biological aging through lifestyle and science.
Burn – Herman Pontze (Get a copy)
Reveals how humans actually expend energy — debunking myths about exercise and calories.
Atomic Habits – James Clear (Get a copy)
The ultimate guide to tiny, consistent actions that lead to massive, lasting change.
8. The Real Bottom Line
At 46, I’ve learned that health isn’t about perfection. It’s not about how you look for two months; it’s about how you feel for twenty years.
The goal isn’t endless restriction. It’s intelligent awareness, understanding how your body interprets what you feed it, how you rest it, and how you treat it under pressure.
If there’s one thing I want you to remember from all this, it’s this: Your body isn’t your opponent. It’s your longest partnership.
Feed it wisely. Move it regularly. Let it sleep deeply. Keep it calm when life isn’t. And, above all, listen to its feedback instead of fighting it.
Because when you treat your body like a co-founder instead of an employee, it starts working with you, not against you.
And if counting calories really worked, Excel would have been the world’s most successful gym.
Watch: Dr. Jason Fung — Why a Calorie Is Not a Calorie
Dr. Jason Fung shreds the "Calories In, Calories Out" lie in this 12-min video. Obesity isn’t about laziness or overeating—it’s insulin forcing your body to store fat like a doomsday prepper.
He shows why calorie-restricted diets fail: your metabolism crashes, hunger explodes, and fat stays locked. Same 100 calories from cookies vs eggs? Cookies spike insulin and trap fat; eggs don’t. Food is hormonal instructions, not fuel.
Core message: control insulin (via low-carb, fasting), not calories, to actually lose fat. Brutal, clear, and flips everything you were told upside down.
“The problem isn’t that we eat too many calories. The problem is that our calories come from the wrong places.” — Dr. Robert Lustig
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