Blog Post

3 Ways Dieting Could Be Slowing Your Metabolism

Scales and waist circumference

Having trouble losing weight?

Unless you are a lucky minority, most people who have attempted weight-loss have faced the horrid weight-loss plateau. This refers to a stop in weight-loss for an extended length of time despite no change in observed behaviour (e.g. diet and physical activity).

Anyone who has gone through this will understand how frustrating and discouraging it can be.

Your personal trainer thinks you’re lying,
your friends think that you have messed up your metabolism and
you feel frustrated that the scale is not changing.

Lucky science is able to provide some explanations that hopefully can help us make smarter decisions to handle this. This blog will investigate the big culprits for weight-loss plateaus.

You Are Unknowingly Eating More Than What You Think

Before getting into the tips, it’s worth mentioning this point even though isn’t a way that dieting could be slowing down your metabolism. In many cases, a weight-loss plateau is simply an underestimation of the total amount of food eaten per week.

There are several ways that this can happen. Not accounting for snacks and being unaware of food eaten during ‘less stringent days’ (the weekends) are potential reasons.

Even in those sure that they are not eating more than planned can still fall victim to underestimating food intake.

In one of the largest diet studies ever conducted, the 600 participants consumed an extra 200 calories at twelve months after starting versus at the beginning.

This isn’t a shock finding since dieting leads to appetite stimulation. And this finding is replicated in some way in the majority of studies. This increase in hunger from when someone first starts dieting can then cause unintentional increases in food eaten over time.

This may cause a weight-loss plateau without being aware of a change in food intake.

1) Your Body Is Using Less Energy Than What It Did Before

In those people certain that they aren’t eating more than expected, there are other likely reasons.

It is likely that their body is using less energy than it did from when they first started dieting. The new amount of energy that the body is using now matches the total amount consumed which explains why weight loss has stopped.

This still doesn’t explain how someone uses less energy than they did before dieting.

The term ‘metabolic damage’ is commonly used to try to explain this phenomenon. This refers to some sort of permanent damage to the metabolism that results in less overall energy used per day.

Although some practitioners determine this from anecdotal evidence. The available science does not support that this is a likely route for most people.

Studies looking at recovering anorexic patients have found no permanent damage in metabolism once body fat and muscle was proportionally gained.

That being said, while metabolic damage may not exist, metabolic adaptation is a real phenomenon to be aware of. This concept covers a decrease in total daily energy expenditure that occur due to more than just the change in total body mass.

2) Eat Less, Move Less?

The biggest culprit for less energy used per day is actually decreases in non-exercise activity thermogenesis (NEAT).

NEAT refers to the energy used from activity that isn’t ‘purposeful’. This might include conscious and subconscious activities such as fidgeting, walking and standing.

In some people dieting, their motivation to do ‘everyday-activities’ goes down. This could be conscious activities such as driving to the shops instead of taking the five-minute walk.

It can also include activities that you have little to no control of. Overall, you may move less during the day when usually it’s hard to keep still pre-dieting.

All this leads to a decrease in energy used throughout the day. This response seems to change from person to person and is more clear in larger weight loss attempts – around 10kgs.

This is part of why for those looking to lose a significant amount of weight, it could be worthwhile considering diet breaks.

3) Weight-Loss Isn’t All Fat

It is rare to lose a substantial amount of weight without some of that coming from muscle. The reality is that for most people trying to lose body fat, they will likely also lose some muscle. This is because when dieting the body will also use muscle for energy which causes muscle loss.

Muscle is metabolically active tissue. This means that to maintain muscle, your body uses energy. Technically fat requires energy to be maintained as well, but it is a lower amount.

As an estimation, muscle burns around 12kcal/kg/day, while fat burns around 4kcal/kg/day. When you look at it in that context, it isn’t a massive difference, but it certainly makes a difference.

When someone loses weight, they now reduce the amount of muscle. This thereby reduces the amount of energy needed to maintain it.
As a result, the body uses less overall energy and can balance out the ‘energy in, energy out’ equation.

The Big Picture

Weight-loss plateaus are complex. It is very rare that all this is a cause of just one factor.

Instead, there are multiple factors that are not limited to those just discussed that contribute to the weight-loss plateau.

By Matthew Benetti

Matthew Benetti is a Masters of Nutrition and Dietetics student at Flinders University. He has previously completed a Bachelor of Nutrition and Food Sciences. Matthew is interested in most things’ nutrition and food. Having grown up in an Italian family, food has always been more than just something you shove in your mouth, but also a way of bringing people together. With experience as a competitive amateur boxer, Matthew is also interested in combat sports and providing long lost evidence-based practices to these sports.