There’s no shortage of miracle-diets out there promising that you can lose 1pound a day, 10 pounds a week, 100 pounds in 3 months, you name it! Any diet making promises like this is either ridiculously unhealthy, or (more likely) full of crap. (Book-covers and diet programs sell better if they promise utterly ridiculous results). The sweet spot is 2 pounds per week, here is why.
So what’s wrong with losing weight that fast?
Your body is genuinely only capable of metabolizing stored fat as an energy source at the rate of about 2 pounds per week. (That’s 7,000 calories worth of STORED fat that you are forcing it to use as an energy source!!). That’s a biochemical limit and there’s no getting around it. (The enzymes in your body that mobilize fat-stores simply can’t work any faster!)
So if the scale is moving FASTER than 2 ponuds per week, one of two things are happening:
1. You are losing water weight:
This is actually really common in the first 5 to 7 days of any diet that restricts carb-intake. (And any diet worth anything is going to restrict carbs in some way). You could lose 4, 8, even as much as 12 pounds in the first week depending on how overweight you are when you start. There’s a whole chemical reason behind that related to burning through glycogen stores that I probably don’t need to get into here.
In other words, don’t panic if you drop a ton of weight right up front. This is normal. And in some cases, it’s extremely motivating to have such big losses right out the gate! Take it and run with it!
Remember, these miracle diets that promise “10 pounds of weight loss in 7 days” are effectively doing this same trick: they shed the water weight, not the fat. When you see the scale move, you assume it worked. Except you didn’t actually lose any fat, the weight comes right back on as your body goes back to retaining the normal levels of water. It’s nothing more than a parlor trick. (Professional boxers and wrestlers do this all the time to make their weight-class right before weigh-ins. If you pop some water pills and the weight drops right off!).
But there’s another possibility if it’s not water weight, and it’s a problem.
2. You are burning muscle
If you’ve been on the diet for more than a week or two and the weight is still coming off at a rate faster than an average of 2 pounds every 7 days, you’re burning muscle.
As mentioned above, the enzymes in your body that are responsible for attacking fat-stores, extracting the fat, and moving it into a position where it can be used as an energy source, are biochemically incapable of mobilizing more than 2 pounds of fat per week. Period.
So, if your body can’t physically burn the stored fat fast enough to get you the energy you need, it’ll go after the next-best thing: muscle. (I explain the differences between fat/protein/carbs as energy sources here, worth a read if you haven’t seen it yet).
But we want our muscle. The more muscle we have, the better our metabolism works. In a roundabout way, the statement “muscle burns fat” is entirely accurate.
So in that sense, if we’re burning muscle, we’re going backwards. We’re LITERALLY slowing down our metabolism! This is explained over here, where I talk about why most diets simply don’t work, and more importantly, why they’re actually DAMAGING your metabolism!
To be clear, if you’re trying to lose a huge amount of weight, there’s simply no way to avoid also losing SOME muscle in the process. But, our goal is to lose as little as possible. So sticking to that speed over the long-haul is extremely important. Note that it’s okay to average this measurement over 2 weeks or even 4 weeks. (In other words, if you’re losing 8 pounds every 4 weeks, or 16 pounds every 8 weeks, on average, then you’re right in the strike-zone, even if the ACTUAL numbers vary from week to week.)
Conclusion? Aim to lose NO MORE than 2 pounds per week on average, and if anyone tries to convince you that their diet can help you lose weight faster, run away. Fast! Weight-loss and fitness is a marathon, not a sprint, We’re in this for the long-haul!