Maintaining a healthy level of body fat isn't just about looking good...
As you know... being overweight or obese has also been clearly shown to increase the risk of multiple serious negative health outcomes.
Almost every single person who has an interest in health & fitness is aware of their own body weight/body fat levels...
...and many go through an almost permanent process of trying to reduce excess fat.
Regardless of the underlying reasons for that goal...
aesthetic
health
performance...
...and regardless of how successful you have been in achieving (and maintaining) that result...
...it's a journey that you're probably familiar with.
Short-Term Thinking...
When it comes to strategies to lose excess body fat, you'll typically focus on:
exercise (commonly with the aim of burning calories)
and/or diet (reducing or maintaining calorie intake).
Both do of course play a vital role, as getting one or both right can help to produce an overall calorie deficit...
...in other words by influencing 'calories in' and 'calories out' you can help ensure that over a specified period of time, your body burns more energy than you are putting back into it... ultimately leading to overall weight loss.
Technically... this works.
But it's easy to oversimplify the concept... for example, when most people talk about 'calories in', they are referring ONLY to the energy value of the foods eaten.
It does NOT consider:
the 'quality' of your diet
the proportions of the 'macro' and 'micro' nutrients that you are eating (versus what you should be eating)
factors that may affect the digestion and absorption of nutrients
natural fluctuations in biology which, among many other things, may affect metabolism (eg. hormonal changes during the menstrual cycle, or an illness that may affect digestion and/or metabolism).
Equally, 'calories out' often gets reduced to simply "calories burned during exercise".
The idea of "burning more calories than you eat" is more nuanced than this.
For example...
You might spend 45 minutes in a spin class...
...or 30 minutes completing a 5km jog...
You could calculate/estimate/guess that you have burned, lets say, 400 calories during that exercise.
Misconception #1 = thinking that this means you burned an extra 400 calories (compared to zero if you had skipped the workout).
In reality, you're never burning zero calories. The various processes that keep your body running account for a surprisingly high number of calories being burned 24 hours a day anyway.
So the number of additional calories that you burned, considering that the above examples require a fair amount of effort, is relatively small.
Obviously that doesn't mean you shouldn't be exercising.
The point is that exercising purely to burn as many calories as possible during a single workout (a relatively small amount of time in the context of a 24 hour day, or a 168 hour week) could be considered very inefficient at the best of times.
That's if your metabolic rate during the other 23+ hours of the day remained constant...
...and, by the way, it doesn't!
Firstly it will vary throughout a day... a week... and a month depending on a number of factors.
And secondly, your metabolic rate will vary compared to somebody else's... even if you appear to be similar in terms of physique, lifestyle, habits etc.
The point of all of this?
Exercise is a valuable part of the equation when it comes to daily energy balance, and maintaining both a healthy bodyweight and a healthy level of body fat.
But the calories that you burn during a workout are just one factor. And a relatively small one too.
In the long-term, your metabolic rate will be a much bigger influence. And the number of calories that are burned as a result of that metabolic rate is NOT constant!
Sadly, you cannot just sit back and let it maintain your body-composition for you!
Father Time...
Nature has certain laws that you are subject to.
One of those laws is that, unless you do something about it, your metabolic rate will generally slow down as you age (starting from when it reaches it's peak - roughly around the time of puberty/young adulthood).
This will have a major effect on your ability to maintain a healthy bodyweight and healthy body fat levels over time.
Essentially, as time goes by, you have a moving target...
If your metabolic rate does indeed slow down and you do nothing to address it, the number of calories that your body requires in a 24 hour period reduces. And so the point at which consuming excess calories (leading to unwanted weight gain) will occur at a gradually decreasing calorie intake.
(In simpler terms, if you do not address a naturally declining metabolic rate, therefore burning less and less calories, while eating the same number of calories (or more?), then your bodyweight will increase at a gradually faster and faster rate!).
Your total muscle mass is one of the main variables that affects your metabolic rate.
Muscle is "metabolically expensive" - your body burns a relatively high number of calories while;
building
repairing
and maintaining
...muscle tissue.
(Ever heard of the "after-burn" effect of certain types of exercise?!)
Simply put... the more muscle you have, the more energy your body requires to build, repair and maintain that muscle, and therefore the higher your metabolism is!
The potential problem?
Muscle is a "use it or lose it" organ.
Remember, muscle is "metabolically expensive". From an evolutionary point-of-view, this is (or rather 'was') a bad thing... 1000's of years ago, when your next meal would have been far from guaranteed, carrying energy-hungry muscle would have been a disadvantage. We evolved to only have what we need... or to put it another way, to only have what we were using...
...the end result being that if you don't use (in the form of exercise) your muscle tissue, it will simply waste away in what evolution considers an attempt to reduce the amount of energy that your body wastes and reduce the risk of you starving to death!
Of course... in 21st century Britain, we generally have the opposite problem (an abundance of calories)... but our bodies have yet to evolve to this new scenario.
Secondly... it generally becomes harder to build/maintain muscle mass as we age. Sarcopenia (involuntary age-related muscle loss) typically leads to a 3-5% loss in total muscle mass per decade, from the age of approx' 30 years old.
And if that wasn't enough of a hurdle, being female typically means having a lower proportion of muscle mass in the first place... so the gradual reduction will likely seem like an even greater obstacle to the body that you actually dream of!
Whichever way you look at it... avoiding a significant decrease in your metabolic rate will make a huge difference to your ability to maintain a healthy body shape... and the earlier you address the problem, the better!
What Is The Solution?
It is vital to understand that age-related muscle loss is NOT entirely out of your control.
In fact, slowing/preventing the decline of muscle mass should be a top priority for long-term health and optimal body composition.
But it does require a conscious effort to do so. Unless you have a VERY physical job/lifestyle, including plenty of heavy lifting, you are unlikely to achieve this outcome by accident.
The first step is to ensure that you are exercising in a way that promotes the retention of healthy muscle as much as possible...
...and as soon as possible!
"USE it, or LOSE it!"
Whether you like it or not, this means resistance training...
using weights (free-weights or machines)
resistance bands
bodyweight etc...
...it doesn't matter whether you do your resistance training at a gym, at home, in a CrossFit "box", or anywhere else...
But it DOES need to be done.
This often contrasts the typical approaches to weight loss strategies in the gym , or on the road when everybody starts jogging (again) after Christmas...
HIIT
jogging/running
spin classes
aerobics classes etc...
...are typically seen as "calorie burning" activities.
This is technically correct.
But as I said earlier, this is based on very short-term thinking. Burning a few extra calories per day/week ends up being relatively useless in the long-term if you are simultaneously experiencing a declining metabolic rate, accelerated by muscle loss.
Obviously that does NOT mean you shouldn't be doing these types of exercise... they have many, many other benefits.
But as a method of maintaining/building muscle, they will not have the desired effect alone...
...add in your resistance training as a matter of priority!
You also need to ensure that you are following an effective resistance training programme.
Randomly throwing some light weights around might represent progress for the first week (if you're lucky). But for genuine, long-term results, you'll need a structured plan.
At the very least, that includes knowing which exercises you should ideally be including, when/how often you're repeating the workouts, understanding the intensity at which you should be exercising and knowing how you are going to progressively challenge your body over the weeks/months/years ahead.
Important: Building muscle is often confused with "getting bigger", "getting bulky" or "bodybuilding". This is NOT the case. If you wish to achieve such a result that's entirely up to you... but absolutely NOT necessary if you are simply aiming to maintain a healthy level of muscle tissue for the purpose of maintaining a healthy metabolism!
The next crucial factor, is of course... nutrition.
Exercise is merely the trigger for muscle repair & growth.
But without the energy (eating enough calories) and the physical building blocks required, your body cannot actually perform the process.
Those building blocks are the amino acids found in the proteins that you eat.
Physical exercise, especially with the aim of maintaining or building muscle, increases your protein intake requirements (see the chart below - Source: examine.com)...
Fail to meet the requirements, and you will be limiting the ability of your body to repair your muscle tissue... (you can't just make muscle out of nothing!)
The Bigger Picture
Maintaining muscle mass is clearly crucial for optimal body composition.
That outcome alone probably appeals to most people.
But if you need a further nudge to take action, consider the following too...
Most of us will want to maintain a high quality of life as we age.
Failing to maintain muscle mass, and therefore muscle strength, greatly increases the risk of falls and of generally having poor balance and physical strength. In older age, that could mean a greater risk of injury and greater dependency on others for daily tasks.
Getting ahead of the curve NOW and building muscular strength will delay or possibly even prevent a decline that significantly reduces your ability to live independently in the future.
And remember, the longer you wait, the harder it gets avoid a decline that you later regret.
Similarly...
...by adding regular, consistent resistance training to your lifestyle now, you may reduce the risk of developing osteoporosis - the weakening of bone tissue that increases the fragility of bones and ultimately increases the chance of a broken bone due to a fall or impact.
Again, if you want to utilise exercise to help avoid this scenario... your best strategy is to start as early as possible.
According to the NHS...
"Osteoporosis is a health condition that weakens bones, making them fragile and more likely to break. It develops slowly over several years and is often only diagnosed when a fall or sudden impact causes a bone to break (fracture)".
The TLDR Version ...
your metabolic rate refers to the number of calories that your body requires in a day
it naturally declines with age and inactivity
steady cardio does have many benefits for health, and also contributes to 'calories out' if/when aiming to achieve a short-term calorie deficit/balance
however, on it's own, it is unlikely to help address the natural decline in your metabolic rate (unless you infinitely increase the volume of exercise (extremely inefficient))
your total muscle mass is a key component of your metabolic rate and will reduce with age if not maintained via exercise, nutrition and lifestyle
resistance exercise (when following an appropriate programme and diet), helps to build and/or maintain muscle mass. This will help to maintain/increase your metabolic rate
you do NOT need to be "bulky" to have a healthy level of muscle mass
to sweeten the deal - muscle (and bone) strength is also absolutely vital for healthy ageing.
