Generation Immediacy take note. The energy trade offs of acquiring a slimmer body tomorrow

A craftsman doesn't rush their work. They plan what they're going to create, acquire the tools for the job and already have the skills to deliver their vision. It’s the same thing when putting together a well thought out nutrition plan with a goal, tools (nutritious food) and skills (consistent habits). You can take your time (like our craftsman) OR you could take a hammer and blunt chisel to a piece of rock and start hacking away as fast as possible to get an end product to sell to the public (those topless selfies we’ve all seen on social media). As bonkers as that may sound, that's what diving in to a quick 'transformation' can be like on the body for most people. In this article, I'll explain how the body responds to intense bursts of weight loss without you realising it. You can then decide how to plan any future attempt at fat loss.

News and the media moves so quickly nowadays and because of that, we often consider it at an emotional rather than intellectual level. We're overloaded from information sources all around us, it's a struggle to keep up half the time!

This forces us to skim things, become interested in the stuff which sparks a reaction or resonates the most and maybe, just maybe, lose sight of the important things which don't necessarily stand out or get lost in the noise.

Specifically on nutrition, is it therefore any wonder that people jump from diet to diet and transformation to transformation? People basing decisions on what they've been told is the best approach or what has worked for someone else?

After all, who has time to sit down and quietly consider which way of eating and training is best for them, based on past experiences? And then patiently put that plan in to action over a period of years? Not likely.

BUT. In the world of poorly planned transformations, it’s not uncommon for people to use severe calorie restriction for long periods of time. If that phase is too long (like in your typical 8-12 week transformation), then the body is forced to adapt. All it really cares about is preserving life (quite right too). But how does it do that?

For those of you who like to do their own research, go look up ‘Adaptive Thermogenesis’. This is the major reason why fat loss becomes harder and harder the longer you spend in a calorie deficit. And worse, once you’ve completed your transformation, you’re primed to regain the weight you’ve just lost. My mission - to help you understand this even just a little bit, so you’re better placed to maintain your new body after going through the uncomfortableness of dieting.

So imagine you’ve just taken delivery of your first self-drive car (a glimpse in to the future I know). You jump in and drive yourself to the motorway. You start your journey just below the speed limit (calorie deficit) and then press the magic button (a big red one I would guess) for the car to take over at the same speed. You sit back, relax and know that you’re moving in the right direction (losing weight/fat).

After a while, the car knows its battery stores are becoming depleted so it starts thinking for itself, working out the most efficient speed to drive at and unwittingly to you, starts making changes (adaptive thermogenesis). It slows down slightly (reduced thyroid output), not much, but enough to save a bit of energy. You’re still moving (getting slimmer).

You realise you need to go see a friend before your first destination so reprogramme the car to take you that extra distance. Because you’re now going the longer way round (or moving in to more than 2 weeks of body transformation) the car slows again, and again, and again, still slowly without you noticing.

You stop regularly to recharge batteries and still use the same amount of energy (food) to top up. Whilst you’re moving, you just go along for the ride. You’re busy in the car doing your work, catching up with family and friends and all the other things that make up life.

Getting in to the second half of your trip, you think you’re not moving as quickly as you were (losing weight more slowly) but you’re still moving so stick with it. You’re journey gets longer and longer and slower and slower because you didn’t read the manual and don’t know how to speed things up. You finally get to your destination late, tired and frustrated with how long it took. Silly car.

So bringing this back to the human body, how does this kind of slowing down and using less energy over time actually happen? Research studies have implied that a 10% or more reduction in body weight equates to roughly a 20-25% decline in daily energy used. For the average person, that’s almost 400 calories less per day than when they starting their weight loss effort, and just to maintain what they have.

Most of this energy reduction comes from things you can’t see, like a 20% increase in the efficiency of muscle cells when you’re simply walking around. A slowing of your heart rate and the amount of energy you use when resting (sitting at your desk, watching TV, sleeping). Studies have also shown that these changes can start within just 4 days of starting a weight loss effort! 

Not only does the amount of energy you are using go down, but the body also finds ways to try and increase the amount of energy (food) which is being put in. It does this by changing your hormone balance and using hunger signalling and making you feel less full after meals (through leptin and ghrelin) to drive you to eat more. When you’re in a calorie deficit for too long, all your body recognises is starvation and so wants to bring back balance to maintain life.

Thankfully, the above scenarios can be reversed with a short calorie surplus and within a matter of days but this need to be well planned for to avoid binging. Hopefully this shows you that a long term dietary approach which is neither in a deficit nor a surplus for too long (but fluctuates between the two) can be a very effective way of maintaining a heathy metabolism and prolonging your fat loss efforts.

People want results tomorrow (or in the worst of cases, yesterday)! Its my job as a coach to help you understand the impact of wanting to undertake drastic weight loss and find alternatives to make constant change sustainable.

So the next time you think about going on a body transformation mission, just be mindful of what you’re going to put your body through and come up with a plan to address the overeating binge mentality which often surfaces following extreme dietary restriction.

Written by Ben Lawrence, Precision Nutrition Certified Coach



  1. Learney, P, 2014. N1 Nutritional Programming: The Fundamentals of Nutritional Programming. 1st ed. London: ACA Publications.
  2. Michael Rosenbaum and Rudolph L. Leibel. 2010. Adaptive thermogenesis in humans. [ONLINE] Available at: [Accessed 1 November 2016].
  3. Looks A.B. and Heath E.M., 1994. ’Induction of Low-T3 Syndrome in Exercising Women Occurs at a Threshold of Energy Availability.’ American Journal of Physiology 266.