Have you been trying to lose weight and then been surprised when you hop on the scales and your weight has actually increased?


What kind of trickery is this?


Has your diet failed? 


Is your metabolism “broken”?


Should you just pack it all in now?


Well no, because weight fluctuations are completely normal and expected to happen.


Let’s find out why.

Are You Ready To Kickstart Fat Loss?

Why Weight Fluctuates

Your body weight is made up of more than just the fat you have.


You also have a pretty heavy skeleton, muscles and organs too. Now whilst these won’t contribute to day-to-day fluctuation on the scale, there are a few things that will.


The key culprits being:

  • Water
  • Stored Carbohydrates 
  • Food in the digestive tract


Let’s take a look at each of these.


Your body weight is made up of 50-70% water (towards the higher end for men, and lower end for women).


When it comes to fat and muscle mass, water makes up around 73% of muscle mass, and only 10% of fat mass.


These water levels in your body also aren’t fixed, they’re in constant fluctuation as you sweat, urinate, defecate, respire, hydrate and undergo numerous processes in which your body monitors and controls fluids.


Key variables that play a role include hormonal changes (especially in women during the menstrual cycle), the types /amount of food and drinks you consume (salt being a factor), and changes in exercise habits.


Another reason that also affects water stores in the body, is your stored carbohydrates.

Stored Carbohydrates (Glycogen)

Carbohydrates are a fantastic source of energy, so much so that your body stores these for later use.


The stored version of carbohydrates is called Glycogen, and we store the majority of this in our muscles and liver.


We call upon these stores when we need a fairly immediate source of energy that enables us to work and high intensities. 


  • The liver stores 80-100g of Glycogen. 
  • The muscles stores 400-800g of Glycogen

Naturally there is variation as we all come in different shapes and sizes.


Now the kicker is that for every 1g of Glycogen stored, it’s bound to 3-4g of water (which means we also store that).


So if we take a middle of the road approach and say you store:

  • 90g of Glycogen in the liver + 270g of water (totalling 360g of weight)
  • 600g of Glycogen in the muscles + 1800g of water (totalling 2400g of weight)

That equals 2.76kg (6lbs) in which your weight can fluctuate.


As your constantly consuming and expending energy, these stores will fluctuate on a daily basis, as will the water stored with it.

Food Stores

One things that’s often forgotten is that you usually will have food in your digestive tract, either partially digested or ready to be expelled as faeces.


These really depend on how much you eat, the amount you defecate and types of food you eat that may affect transit time (i.e., fibre vs no fibre).


But the point is, these will also be in fluctuation as your body is constantly processing and digesting what you consume on a daily basis.


No surprise then that this also contributes to your body weight.


Perhaps you just need a big dump…

Why You (Probably) Didn't Gain Fat

When it comes to gaining fat, 1lb of fat is equal to 3500 Calories.

So, to gain 1lb of fat, you must eat 3500 Calories over your maintenance calories (the number of calories to maintain your weight).


You can figure out this number by reading about your TDEE.


Let’s say your maintenance calories are 2500, and you’ve created a 500-calorie deficit per day leaving you with a target of 2000 calories per day (as you’re trying to lose weight).


Side note: 500 calorie daily deficits are often used as 500 x 7 (the days in a week), is equal to 3500 calories (so aiming for 1lb fat loss per week). This is often considered sustainable and manageable for most people. However it is also important to note that as your weight decreases so will this calorie deficit.


So, for you to gain 1lb of fat overnight, you need to eat 3500 Calories over your 2500 maintenance calories. That’s 6000 calories in one day! 


But as you’re currently eating in a deficit at 2000 calories, you’d need to eat an extra 4000 calories to reach that 6000-calorie figure and put on 1lb of fat. 


Those extra cookies aren’t seeming so bad now are they.


Armed with that information, does it seem feasible to you that weight fluctuations of more than 1lb are due to an increase in fat stores?


Whilst hitting those sorts of numbers is definitely doable (we all love a dominos two for Tuesday), that extra chocolate bar or packet of crisps you ate isn’t making a dent in those sorts of numbers. 


So, don’t panic, weight fluctuations are completely normal, and it’s most likely not an increase in fat that’s made the scale move

How Much Can It Fluctuate?

Well as always, it depends.


We all come in different shapes and sizes, and the bigger you are the more your weight will fluctuate.


However,  weight fluctuations of around 6lbs are common and this could even go higher depending on the variables explained above.


To get an understanding of your weight. I’d recommend taking an average over 7 days to get a true reflection. 


Simply weigh yourself every day, in the morning at the same time (ideally after a trip to the toilet).


At the end of the week, total each day together and divide by 7 to get an average weight for the week.


If you are trying to lose weight, then do the same thing the following week.


You can then compare these averages and if they trend downwards, you are losing weight (most likely that pesky fat).


Whilst this is the most reliable method, you can also apply this method on a 3-day approach doing Tuesday, Wednesday and Thursday.


This will still account for fluctuations but isn’t as laborious as the every day approach.


If you don’t like weighing yourself that often, then no problem.


Simply being aware that your weight fluctuates and armed with the information in this article, you can take the number on the scale with a pinch of salt.

Are You Ready To Kickstart Fat Loss?

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Sam is a Personal Trainer, Online Coach and Fitness Educator with background in achieving results for a variety of clients. Sam now specialises in Pain Free Performance, helping people across the world to achieve their goals safely and effectively. 

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