Why your weight changes | Balance

People who are trying to lose weight may find that their weight fluctuates from day to day. This is normal and doesn't mean that they are not losing fat. In fact, studies have shown that people who weigh themselves regularly tend to be more successful at losing weight and keeping it off.

Understanding how weight change works and how rapidly you can regain “real” weight (in reference to bodyfat) can help to put your mind at ease and free you from these worries so that’s exactly what we’ll be covering today.


How weight change works

Outside of changing body composition at a steady weight (described as “body recomposition”), almost all contributions to body fat gain (and also why body fat has been lost) can be explained by changes in body weight.


If we gain weight (especially over time), it is likely that some of that will be fat gain. However, short term changes in weight, which many associate with fat gain, can be down to a whole host of reasons, including;

  • Changes in levels of sex hormones

  • Increased fibre and food volume intake

  • Needing to go to the bathroom

  • Changes in body water

  • Inflammation (either by injury, exercise induced damage or some other contributor)

More gradual change in bodyweight is a greater indicator of “real” weight gain i.e. increases in lean body mass, fat mass, bone density etc.


As it relates to lean body / muscle mass and fat mass (and in some context dependant cases, bone density), changes in these groups is dependent on a very basic principle; energy in vs. energy out.


Or, if you’re more familiar with this equation; calories in vs. calories out.


Quite simply, if your goal is to lose weight, then you’d need to consume less calories than the number required to maintain your weight.

If your goal is to gain weight then you’d need to consume more calories than required to maintain.


If your aim is to maintain your weight and focus more on body re-composition then you’d need to eat at a calorie intake around your maintenance and focus more so on macro splits and nutrient timing.


And that’s how weight change works in a nutshell. It’s relatively straightforward (it’s just applying the calories in vs. calories out principle can be difficult in some cases), and not as scary as you’ve been made to believe. So, then the question arises, “well, how quickly will I regain all the weight / bodyfat I’ve lost!?


How quickly can you regain lost bodyfat?

The speed at which you could regain any bodyfat is dependent on the net balance of energy intake i.e. did I consume more energy than I spent and, if so, how much of that will go to fat storage?

As highlighted previously, not every single calorie consumed over your maintenance amount will go straight to fat storage; if the body doesn’t burn it off through increased activity / heat it may also divvy it off to use for muscle building or some other more beneficial function.


Coming to peace with bodyfat regain involves understanding it and, to understand how quickly you could regain bodyfat, you have to first consider how much you can regain in one day and there are quite a number of factors that play into this;

  • Your TDEE (Total Daily Energy Expenditure)

Essentially, the amount of energy you expend each day.

  • Your existing levels of glycogen storage

These are the body’s internal stores of carbohydrate; found predominantly within muscle tissue and the liver.


The more glycogen depleted we are the more of the food taken in will be stored as glycogen as opposed to fat.

  • Your dietary composition that day

Studies have shown that protein overfeeding, or the consumption of a high protein diet, may not result in a gain in body weight or fat mass, both short and long-term, despite consuming calories that exceed your perceived maintenance intake.


In a study investigating differences in fat storage following overfeeding between carbohydrate and fats with a 50% calorie surplus it was shown that, after one day of overfeeding, those who overfed on carbohydrate stored only 10% of that as fat, whereas those who overfed on fat stored 60% of that as fat.

  • Increases in NEAT (Non-exercise activity thermogenesis) variation

NEAT is simply all the calories we burn thanks to activity which isn’t programmed exercise (such as fidgeting, walking around the house etc.)


This is important to factor in as NEAT varies greatly between person to person (up to 2000kcals a day in some cases!) and increases in response to overfeeding.

  • Your current body composition

Those with greater levels of existing body fat have more adipocytes (fat cells) to store fat. Those who are leaner are likelier to have less. So, leaner individuals may have a reduced capacity to store fat. Your number of fat cells appears to be set at childhood; interesting!


It's difficult to quantify exactly how much weight can be gained / regained in one day but it's likely to be so minimal that it's not worth being concerned over.


It's one of the reasons why we advocate for our clients enjoying themselves during the holidays embracing experiences around food.


Matters of consistency; bodyfat regain is determined by what you do day by day

Reversing any change in fat gain would take no more than a few days of getting back into your regular habits. In fact, you’ll probably be more likely to increase your adherence to dietary and exercise patterns and achieve weight / fat loss at the end of that week rather than net gain.


It is the consistency of overfeeding and or acute bouts of overfeeding that will lead to an eventual, notable, gain in body fat. Studies have shown that, even in groups who revert back to old habits after a diet intervention, the rate of total body weight regain is only a mere 0.04kg a month.


This number decreases even further when the groups are informed about, and taught the skills to adequately track, calorie intake.


On top of that, continuation of exercise, higher protein diets, diets of greater nutritional density / quality and consistency of dieting approach all seem to have a protective affect against weight / fat regain.


Basically, everything you’re already doing is protecting you from regaining back any significant amount of bodyweight / fat.


Concluding Remarks

Weight / fat regain is fairly simplistic in how it works, it’s a simple equation. It is the battle between our ears and not allowing the fluctuations seen day by day on the scale (if you do weigh yourself) to affect our behaviours that is the most difficult aspect of weight management during these isolated times.


Stick to what you’ve been practising; exercise, higher protein diets, more fruits and vegetables and being kind to yourself. The odd chocolate bar here and there won’t have any long-term implications for your weight / bodyfat levels. It may actually help you maintain your weight if it means it staves off a binge and scratches an itch or two. Use food wisely; let it fuel your ambition not hurt it. Keep active, mind your mental health and just keep doing what you’ve been doing. Chances are you’ll come out of this leaner, fitter and healthier than ever!


Find out how our coaching team can help you today



Balance is Northern Ireland's leading nutritionist and dietician coaching team. We work with everyone from Olympians to office workers to help them achieve their nutrition and diet related goals.


Get in touch with us today to discuss how we can help you;

- Beat binge eating

- Lose weight and keep it off

- Take your sports performance to the next level and reach your full potential

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