What does "eating less" to lose weight really mean (and why does it take so long)
There's a basic principle in nutrition that to lose weight, the calories going into the system have to be less than what the system requires to function. The goal here is to trigger that fat you want to melt off to start getting used to fill the deficit for energy requirements.
It's actually a tricky balance, as anyone on a diet will tell you. Eat *too* little for your energy needs, and your system thinks it's starving, heads into what's known as starvation mode, and just stalls out, preferring to burn your muscle than your fat. Eat only a little less than "maintenance," and well, weight loss seems to move in dribs. That expected loss of "1 pound a week" just doesn't happen.
So what's the correct place to be, calorically, for kick starting weight loss?
Before i dive into that, a few caveats: healthy weight loss is not *just* about reducing calories. It's about eating the right kind of mix of foods for you at the right times that your system can make optimal use of that fuel. Think about it: those Skinny Bastards out there can eat anything and still stay lean. On the other extreme, some folks seem to just look at a pizza and gain weight. This doesn't mean pizza is evil; it just means that some folks run hotter and faster in their energy systems than others. It's because of these differences in metabolism that i encourage folks to check out precision nutrition for eating habits that take these differences into account.
To that end, precision nutrition does not start with calorie counting; it starts with habits of eating, and getting eating habits cleaned up.
For most people, that's all it takes for the desired effects to kick in. But sometimes it's useful to do a reality check on our practice, to see, especially if we've been dieting, if we're actually eating *too little* or if, in what we're eating, we're getting appropriate vitamins and minerals (micro nutrients).
So with that caveat in mind, let's take a look at some of the ways appropriate caloric deficit can be calculated.
The following are three ways of calculating caloric deficit. One is sort of the bog-standard way to do this; the other is a wee bit more hypothetical but very interesting. The article closes with some references for where to reality check your own intake.
One rather crass method is simply to cut 500 calories a day to get to the requisite lose a pound in one week. If you're a great strapping man eating 4000kcals for maintenance, 500 is a reasonable hit. If you're a wee gal, that much of a deficit could put you in starvation mode. So let's consider something more gated to who you are and where you're at.
The first reasonable method is this: determine your base metabolic rate and subtract 20%. This was initially proposed by Dan Duchaine in Bodyopus. Christine Thibaudeau, a respected body building coach, explains this method in detail in an article called "Gain Muscle and Lose Fat Optimally" The purpose of the approach there is less important to our purposes than a super explanation of the calculations of interest to us.
So let me quote CT directly:
Your BMR is a function of your size, sex, and age. It's also influenced by your metabolic status (hypo or hyperthyroid state for example). We can calculate BMR with the following formulas (by Harris-Benedict):
BMR = 66 + (13.7 x weight in kg) + (5 x height in cm) - (6.8 x age)
So for a 30 year old bodybuilder of 220lbs (100kg) at 5'11" (178cm) it comes up to:
BMR = 66 + (13.7 x 100kg) + (5 x 178cm) – (6.8 x 30)
BMR = 2122 calories per day
BMR = 655 + (9.6 x weight in kg) + (1.7 x height in cm) - (4.7 x age)
So for a 28 year old figure girl of 132lbs (60kg) at 5'6" (165cm) it comes up to:
BMR = 655 + (9.6 x 60kg) + (1.7 x 165cm) – (4.7 x 28)
BMR = 1380 calories per day
Second Step: Factoring in activity level
The amount of calories found using the Harris-Benedict formula is what your body burns every day, even if you do nothing all day. Obviously, the more active you are the more you'll burn fuel. So, energy expenditure will be increased when your activity level goes up.
To get an adequate estimation you need to multiply your BMR by an activity level factor:
Activity level factor
1.2 Very light activity
1.4 Light activity
1.6 Moderate activity
1.8 High activity
2.0 Extreme activity
By sedentary we mean doing nothing all day (sleeping and watching TV).
By very light activity we mean doing nothing physical. Working a desk job or on a computer and not performing any type of physical activity during your day.
By light activity we mean having a non-physical job (desk, computer, etc.) but performing some sort of physical activity during the day (e.g. above average walking) but no hard training.
By moderate activity we mean having a non-physical job, performing some sort of physical activity during the day, and including a daily workout session in your routine. This is where most of you are at.
By high activity we mean either training plus a physical job or non-physical job and twice-a-day training sessions.
By extreme activity we mean a very physical job and daily hard training.
So BMR * Activity Level gives caloric energy requirements for a day. Subtract 20%, and you have the average amount of a daily caloric level for weight loss.
Caveat time again: in terms of thermodynamics, a calorie is a calorie, but in terms of how we process food, it's not quite so simple. You wouldn't eat all your calories as raw sugar (would you?) So our fuel needs are a little more subtle. So after calories are sussed out, determining ratios is a critical thing. I turn again to precision nutrition for guidance on this point, and strongly encourage anyone looking at this to think about basics like: eat protein and veggies at every feeding, whether you eat once, three or six+ times a day; until you know more about your body, only eat starchy carbs AFTER you work out. If you don't work out, and you want to lose weight, don't eat those starchy carbs. Stick with veggies. Lots and Lots of veggies.
MacDonald and Fat Fuel per Pound
SO that's one tool. Another proposal for calculating optimal caloric deficit is presented by Lyle MacDonald, author of the Ketogenic Diet. He had a hypothesis that suggested fatter people would have more of a deficit than thinner people. That sorta makes intuitive sense - feels right, doesn't it? MacDonald talks about finding a paper that looks at this question. It's called "A limit on the energy transfer rate from the human fat store in hypophagia." (Alpert SS. J Theor Biol. 2005 Mar 7;233(1):1-13.) The answer, it turns out, may be a little different.
To cut to the chase, the researchers suggest that fat can provide energy to the body at 31kcals/pound. MacDonald states, assuming normal/moderate activity from the above scale:
So, if you are carrying a mere 10 lbs. of fat, you can sustain a 310 cal/day deficit.
20 lbs. = 620 calories.
30 lbs. = 930 calories
You get the idea and this is not difficult math. Multiply your total fat mass in pounds by 31, that’s how much of a caloric deficit that fat mass can support on a daily basis.
What's interesting is how this means caloric deficit will adjust depending on amount of fat to lose.
To get to that point, we need first to know how MacDonald calculates maintenance level calories: he works it out to 15kcals/pound. So a gal at 147 is likely consuming 147*15kcals or 2205kcals a day. I'm not sure how accurate this is in the real world, but let's continue to see where the calculations end up.
Let me add another Precision Nutrition tip here: that in any weight loss program, it's a really good idea to measure more than just weight on the scale. Especially if you're also working out, you may be gaining (heavier) muscle while losing the (lighter) fat. Therefore, doing girth measures (hips, waist, etc) and body fat measures (7 point caliper/skinfold measures being the most accurate at a BMI of 26 and below; navy circumference more accurate for above 26; DEXA scan most accurate (and pricy) of anything) Not to sound like a broken record but PN takes your through all these measures and calculations. The reason being, as said, the scale may become a less informative measure than seeing your butt tighten up and your waist get smaller and your BF% go down.
Ok so back to MacDonald's review:
Say we have a 180 lb male at 15% bodyfat. He has 27 lbs. of fat, and his maintenance calorie intake is 15 cal/lb or 2700 calories. With 27 lbs. of fat, he should be able to sustain a caloric deficit, from diet alone, of 27 lbs. fat * 31 cal/lb = 837 calories/day. So he could reduce his calories to 1863 (ha! 10 cal/lb) and shouldn’t lose any LBM [that's Lean Body Mass - like muscle -mc ] at that level of intake. He should get a weekly fat loss of just over 1.5 lbs./week [that's calculated roughly on energy required to lose a pound=3500kcals -mc]
If the same 180 lb guy was at 10% bodyfat, only 18 lbs. of fat, he could only sustain a 558 calorie/day deficit (2150 cal/day or 12 cal/lb), he’s down to 1 pound per week. By the time he’s at 8%, he’s down to 14.5 lbs. of fat and a total deficit of 446 calories/day and about 2/3 a pound of fat loss/week. Oh yeah, if he were a fat shit at 30% bodyfat, that’s 54 lbs. of fat, he could sustain a deficit of over 1500 cal/day and lose over 3 pounds per week of pure lard; of course he’d only be eating 1300 cal/day. Again, the above all seem to roughly pass the reality check in terms of what we see in human dieters.
What this means is that as a person loses weight, they lose less weight as rapidly. For the sake of completeness, let's consider the rest of MacDonald's worked example
Our 180 lb man at 15% starts his diet. He has 27 lbs. of fat and can sustain a maximum deficit of 27 lbs. * 31 cal/lb = 837 calories. Assuming a maintenance of 15 cal/lb (2700), his starting calorie level will be 2700 cal - 837 calories = 1863 calories/day. He’ll be losing around 1.5 lb fat/week.
So now we check in 8 weeks later, he’s down 12 lbs., almost purely of fat (we’ll ignore any small LBM losses). His new numbers are 168 lbs. with 15 lbs. of fat = 9% bodyfat. Maximal sustainable deficit = 15 * 31 = 465 cal
Assuming his maintenance is still 15 cal/lb (not automatically a safe assumption), his maintenance requirements should now be 2520 calories. But the adaptive part of metabolic rate reduction has probably dropped him a good 10% below that. So let’s say his maintenance is 2250 cal/day or so. 2250 cal/day - 465 calories = 1785 calories. So, not much of a reduction from his previous 1863 calorie/day diet. Basically, the drop in his maintenance levels over the course of 8 weeks offsets the fact that he can’t sustain as much of a deficit and is now leaner. Of course, his fat loss has also slowed to just under a pound/week.
Now four weeks later, he’s dropped about 4 more pounds of fat. His new numbers are
164 lbs. with 11 lb of fat = 6.7% bodyfat. Maximal sustainable deficit = 11 * 31 = 341 cal
His maintenance will have dropped further, let’s say 14 cal/lb (people’s daily activity tends to go down due to the hormonal changes from extreme dieting) and a 15% adaptive reduction which brings him to 1951 calories/day. Reduce by 341 to get 1610 calories/day. He will need to reduce daily calories by a couple of hundred (from 1785/day to 1610/day) to achieve the maximum deficit but his fat loss will be down to 2/3rds pound per week.
So, what does this tell us? that in these "estimations on estimations" as MacDonald situates them, there's a logic to why people seem to lose less weight as rapidly when they have less weight to lose. There's simply less fat-as-fuel available for daily energy requirements.
How does MacDonald's approach compare with the 20% less?
Let's take a look at CT's 128 pound 24 year old female without too much weight to lose. BMR is 1389kcals/day. With a Light activity, that's 1389 * 1.4. That's 1944 calories for maintenance. This is someone who is *not* working out.
If you are a gal looking at this you may be freaking out right now thinking "how could i ever eat that many calories - just for maintenance" - if you do anything more robust than walk up the stairs, like actually work out IT'S EVEN MORE. If you're eating way down at 1200, and working out and not losing fat it's cuz you're starving yourself and your body ain't gonna give up that fat without a fight. Eat more. See what happens.
Ok, anyway that's our gal at maintenance. at 20% less (388.42) that's 1556 kcal per day. That's 2716 calories a week - 784 shy of a pound. So that's three quarters of a pound lost a week. Not at all the pound a week, is it? So to lose, say 5 pounds will take close to 7 weeks. Sounds long, eh?
With MacDonald's approach, we get 15*128=1920. So pretty close to the result we have for an lightly active person (MacDonald gates this amount of calories per pound based on activity too - so a less active person would be a lower amount of cals/pound. Check the article for more details, but we'll stay with this figure as they're more or less aligned).
With 5 pounds to lose, that's 5*31kcal/pound = 155 kcals a day or 1765 total a day. That's less than half the calorie reduction of the 20% calculation. In this case, it will take more than three months to lose 5 pounds - in fact longer, as the less there is to go, the fewer the calories per day reduced and not lose lean body mass (don't want to lose muscle, which is what losing lean body mass means).
So let's look at 6 weeks in and say 2.0ish pounds have been dropped (155*7*6=6510, not quite 7000 for 2lbs)
We're now at 126 with three pounds to go, that 3*31=93 calories per day less than 126*14 (to use MacDonald's figure, assuming some drop in metabolic rate from dieting) =1764-93 = 1671. So to keep the weight loss happening, the input is progressively lower but the drop tapers out, so it's now longer again to lose those last few pounds.
And doesn't that just sound familiar. Your mileage may vary, but based on the number of folks i've encountered who really do have just a few pounds to lose, it does seem to take FOREVER. It becomes very hard to stay the course of being on top of their nutrition.
This is where and why for those last few pounds, some people get impatient and go extreme - they do some kind of extreme (super high fat no carb) diet, or fast. Or they take drugs.
The other response is to just be patient and stay the course; get a lot of support. Or find a diet that will let you go nuts safely, and will let you come back without a horrible rebound. John Berardi has a diet for those last few fat percentage points. It's called "the Get Shredded Diet" (yes yes, available in precision nutrition). It's only recommended for either guys who are more or less into single digit body fat numbers, or gals who are into loooow teens or non-teen double digits. Great care is taken to ensure that LBM is not compromised. Some folks make LBM gains, too. The interesting thing is that it takes as long to come out of that diet as it does going into it so there's no sudden weight gain rebound. Berardi says he only does it once every two years or so, and more for personal reasons than any competition need.
So where does this take us?
It would be interesting to see the numbers comparing folks at different stages of their weight loss mission to be able to see just how far the cut 20%'ers get - do they achieve their goals within the predicted time for that amount of fat loss? or do they not? and if not, but what %?
So, go ahead and go for the 20% reduction as a place to start - after you've gotten clean on your intake with something like PN - if you're not eating right, what's the point? less crap is still crap. CT's article cited above also goes into the intriguing world of what's called Carb Cycling to maximally effect weight loss for those who are really working out - not a starting strategy for someone who is only up to lightly active.
I guess the point is, despite the unbelievable length of time MacDonald's calculations show for losing such a little bit of weight, anecdotally, i believe it. That's certainly where the struggle is.
I hope, though, that from looking at this post, you'll have a clearer idea of both where you're at and why in your own weight loss path.
If you're still looking for some nutrition guidance, check out Precision Nutrition Strategies for Success. It's free, gives a great overview of the program and its 10 habits approach, and you can decide if you want to delve further.
Partial Reality Check
If you want to check out where you're at right now in terms of your caloric input, try Fitday.com the web site or (my preference) the desktop software application. Enter a log of your eating for a week, not only to check your calories, but what your carbs/protein and fats ratios are, as well as your daily micro nutrients. More on these in a later post.
You may say, but wait, what ratio of carbs/proteins/fats is right for me. The precision nutrition answer would be, well, first get right with basic nutrition habits as in the precision nutrition success strategies, and see where that takes you before getting intrigued with the micro/macro. Having done all that, you need more tuning, time to connect with the Plan Stan. A quicky answer would do you a disservice.
Hope this helps.