…but did you really?
The answer kind of depends on what you mean by “muscle”. Most people think of their muscles as big (or perhaps not so big) blocks of…well…muscle.
In actuality, only about 19% of the weight of a muscle is made up of contractile proteins. The overwhelming majority (75%) is made up of water, and the remaining 6% is split between things like glycogen, fats, minerals and other biological tomfoolery we don’t need to worry about.
You can probably see where this is heading. If you’re down 0.1kg of skeletal muscle mass this week, it’s way WAY more likely that what you’re seeing is a swing in the water weight of your muscles, rather than the protein weight. Water content can change from day-to-day and week-to-week quite a lot depending on your hydration levels and energy stores.
All that contractile protein your body has built up will not be lightly disposed of. It cost a lot of time, energy and effort to create in the first place, and your body will need a really good reason to get rid of it. Afterall, as far as your body is concerned that tissue could be put to productive use throwing spears to acquire more food, running away from predators, or looking buff to attract a mate and propagate your genes. It’s quite useful, and it’s difficult to get more of it.
Keeping your muscle mass is an extremely good idea from a biological perspective, so you’re biologically set up to do it if you give yourself even half a chance.
Now, are there situations where you might genuinely lose contractile protein? Abso-bloody-lutely.
In fact, there are 4 main ones. If you’re seeing an ongoing TREND of losing muscle mass each week, you’re probably doing one or more of these things. I’d recommend you stop that.
1. You’re starving yourself
If you’re WAY underdoing it on your total calorie intake and crash dieting, your body basically thinks there’s a famine you need to survive. Muscle costs energy to maintain, so getting rid of some it seems like a good idea for now so that you actually live long enough to do anything useful later on.
If you’re trying to lose fat, you shouldn’t ever be really hungry. You should be complaining that you’re having trouble finishing all the lean protein, vegetables, fibrous carbohydrates, fruit and healthy fats we’re telling you to eat.
You might have to deal with some cravings for junk food…but that’s not the same as being hungry.
2. You not eating enough protein
Likewise, just maintaining your muscle mass where it is requires a certain amount of protein each and every day.
Muscle cells are in a near-constant state of turn-over. In fact they get broken down and built back up every 7-15 days. They don’t just sit around doing nothing.
So if you don’t eat your 1-2 palm sized servings of protein-dense foods 3-4 times per day, and you’re a physically active person (particular one who lifts weights), protein break-down can indeed exceed the rate it’s being built back up at. Not good.
If you get nothing else right about your diet, make sure you’re eating enough protein every day.
Cook the food, drink the protein shakes, keep a stockpile of protein-dense snacks in your fridge. Do what you’ve got to do to get all your portions each day.
3. You’re not lifting weights
If you have a larger-than-average amount of muscle mass, but don’t do any heavy weight-bearing activity for a while, your body gets the message that maybe all this energetically-expensive muscle mass hanging around the place isn’t actually that important and could probably go.
I include this reason mainly for completeness, since this is only really a worry if you’ve already got say 130%+ of the normal amounts of muscle mass. If you’re in that territory, chances are you really LIKE lifting weights, so you’re probably not going to stop doing it.
4. You’re already really, really lean
Another rare one, but for gents trying to diet down into single-digit bodyfat percentages, or for ladies trying to get below 16% bodyfat, some level of muscle mass loss is inevitable. The lower you go, the more you’ll have to lose too.
For most people, this is is a pretty unhealthy level of bodyfat to try and hold onto for any length of time, and the dieting required to get there will crash all your anabolic hormone levels hard, make you miserable and cause you to hate everyone.
One of the nice reasons to measure your bodyfat percentage is to tell when to STOP dieting. Guys below 10% are typically done, and ladies below 18% are probably done too. Life won’t get any better if you’re leaner than that, and will usually get much worse instead…unless you derive a lot of meaning from stepping on stage in little purple underwear and suchlike…
From that point it’s time time to re-focus and set some new goals!