Fun fact, for my day job, I research human behavior and how it impacts the technology we design, and I’ve learned a lot about what motivates behavior and what patterns will ensure people will stick to their commitments. The biggest lesson I’ve learned through this research (and through personal experience) is that your strategy must help nudge you toward desired behavior, and use friction for unwanted behavior.

But, this has its limits, too. Even if you have the most foolproof plan, nudging is only as successful as your body is physically capable of. For starters, you have to choose a behavior that is realistic and attainable. The problem with most diets and weight loss plans is that people set unrealistic expectations of themselves and their body’s performance.

So, before you go chasing waterfalls *cue trumpet sound from the TLC song* and setting yourself up for a goal that’s unobtainable, you need to have a solid foundation in how the body gains and loses weight. In part 1 of this series, we will talk about how metabolism works.

Part 1: Your Body is a Factory

Let’s start with a metaphor. Think of the body as a factory with a big-ass tank of energy (sometimes stored as fat… so I guess you could also call it a big ass tank *badum-tssss*). The factory (body) uses energy stored in the tank (which includes fat and other cells) to run the factory which creates and fuels muscles. Muscles are responsible for movement, organ function (organs are, themselves, muscles), and the brain and its activity. In short, muscles are the gears of your life, treat them with care!

The body-factory intakes and expends that energy in units known as calories. I’m using calories and the muscle-gears to type this very sentence, to think of these words, to make my heartbeat and lungs breathe. The calories I’m using right now were eaten at some point before my typing, thinking, and breathing. The point is: no calories are bad. They are used at a resting state and slightly more in an active state. The rate at which you use calories constitutes your metabolism.

The Body’s Balance Sheet

How many calories does your body need? Well, if you literally laid in bed the entire day and did nothing except eat, drink, and use the bathroom, your heart, lungs, brain, and even resting muscles are still using energy, creating a baseline caloric requirement to simply live. This is called your resting or basal metabolic rate (RMR or BMR). If the body has more demands placed on it (like any amount of exercise, walking a lot, an injury, sickness, a pregnancy), it naturally needs more calories to keep up, and if you ate just enough to fulfill that basic caloric requirement, you will now be in a caloric deficit.

And when in a caloric deficit – as in, the tank is using a bit more calories than it receives, the factory workers (your cells) will start unearthing fat stores and burning them to fuel daily activity. Unfortunately, if you’re in a caloric surplus (as in, receives a bit more calories than is expended) the factory workers, with all their good intentions, will not simply waste that wonderful, hard earned energy. They will store that energy as either fat or muscle (depending on the rate at which you obtain it)

So, to simplify all diets in the world into a single equation:

Weight change* = calories INcalories OUT
(*total loss or gain of ALL weight – fat AND muscle)

That said, while the math is beautifully simple, caloric count is not the only thing that matters with food intake. How you restrict calories is just as important as the amount restricted.

The Two Supervisors

Okay, back to our body/muscle-factory metaphor. The factory doesn’t simply run itself. It’s manned by two competing supervisors (appetite hormones). Mr. Ghrelin (hunger supervisor) has one job: to send up regular requests for more raw materials (food) unless told otherwise. Ms. Leptin (satiety supervisor) also has one job: let the brain know when she’s received enough material for caloric output for the next several hours, so that the boss can tell Ghrelin his request has been denied.

Think of Leptin as someone who walks the factory floor, waiting to accept deliveries, so it takes her about 20 minutes to get a status update to the boss. She’s a busy lady! Ghrelin, on the other hand, operates largely like a goblin in the dark (hey, think about it… with a name like Ghrelin…) and takes cues from Leptin and the Brain to slow down those requests or speed them up.

Ghrelin and leptin have a complicated, co-dependent relationship, and their primary responsibility as a duo is to make sure the factory has enough energy to run.

(Stick with me here.)

Caloric Intake and the Impact of Yo-yo Diets

If you’ve tried as may diets and food trends as I have, then you’ve probably learned from experience that crash diets suck. And no, it’s not your fault that the diet sucked. Crash diets literally suck the life out of you. Here’s how.

Let’s say that you’ve expended far more than you consume in 7 days (a severe caloric deficit like a grapefruit cleanse or some sh*t, where you lose 1-2 lb per day). Leptin is running around frantically trying to find signs of missing shipments that she is sure she was expecting, based on Ghrelin’s requests and order history, but is simply not seeing. Since Leptin is running about and is decidedly not reporting back to the Brain or Ghrelin… Ghrelin, left to his own devices, will start getting jumpy and would totally be the type to send 7 consecutive SOS text messages to upper management (Mr. Stomach, the COO):

“I don’t know what’s happening boss!!”
“I haven’t seen Leptin anywhere!!”
“We normally get our shipments on time…”
“But it must be getting really bad!”
“We should resupply ASAP!”
“Are you there???”

… and then the Brain (CEO), being tired and underfueled, and annoyed the Stomach can’t deal with this himself, says, “Listen… can’t you just handle it…?” And next thing you know, you’re balls deep into your third bowl of cookie dough straight from the tub (No? Just me? Okay…) replenishing all the calories you “lost.”

Or, alternatively, let’s say you have been in a slight deficit for 3 months now (you’re calorie counting and losing weight at a rate of 0.5-1lb per week), Leptin keeps checking in, saying “Well, we’re not 100% but we’re at like 85% so I think we’re okay, no need for urgent resupply” which keeps Ghrelin and the Brain chilled out. Meaning, you’ll still lose weight, but you won’t be starving all the time. This works great in the short term!

But, after a while, the Brain will tell Leptin, “Well, if things aren’t turning around, we can just operate everything at 85% and that will be our new ‘100%’ – to save resources.” Cognitive output slow a little, weight loss also plateaus, and worse, the body may start to dissolve your muscles and either use them up or turn them into fat, to close the caloric gap and ensure the other organs can function.

Yeah, you’ll survive, but you’ll likely be tired, your overall health may be impacted, and your results will look less like lean muscle and more like “skinny fat” – which is when you’re underweight but lack muscular strength or definition.

As for muscle “gainz”… if you eat at a severe surplus, and also do not supplement with exercise, you will probably see much of that weight stored as fat, rather than as muscle. However, if you eat at a slight surplus, over time, supplemented with “resistance” exercise (like weight training), you’ll probably see muscular gain rather than fat gain.

TL;DR? Take it Easy, Go Slow.

Moral of the story: Eat just enough to meet your caloric needs, and occasionally do brief periods of SLIGHT caloric deficit or surplus, if you must. Your body is a sophisticated machine that’s been built to sustain you for the long haul, and you should treat it like you’re in it for the long haul, too.

Assignment #1: Figure out what your calories “out” look like.
This number will differ based on your age, sex, height, weight, lifestyle and preexisting health conditions.

  • Easiest/Cheapest: Use a BMR and Caloric Needs calculator, like this one
    Keep in mind it is an estimate based on your height and weight, and doesn’t account for health conditions that may be impacting your metabolism. This will help you better estimate how much you should be eating.
  • Most Accurate: Ask your doctor or a professional nutritionist about metabolic testing.
    This is a literal measurement of your caloric output based on how quickly your body turns oxygen into carbon dioxide while in a resting state. You can find these services at a healthcare facility, but they can sometimes be costly depending on your health insurance. However, this knowledge can be invaluable if it helps you manage not just your weight but also your energy levels and overall health.

Once you have this baseline, you can start thinking about the best way to meet that caloric requirement by tailoring your macronutrient ratios.

With that… stay tuned for Part 2: Setting Up Your Plate for Healthy Eating

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