Just wondering whether anyone can point me in the direction of the scientific evidence behind recommendations that for example say that 1200 calories a day is the minimum you should go for?
This (or similar statements) seem to be often quoted, but I've been trying to find out the origins/scientific studies that back them up and basically it's not easy, so thought i'd ask my fellow Chicks!
It seems unlikely to me that if you ate less than this you wouldn't lose weight faster, it also seems unlikely that it's unsafe to eat less than this. For example I would've thought that my current plan of 1000cal max is effective and safe for me to lose weight on (ok, i'm pretty short, so this would help). But I want to read the results of the actual studies that have been done on this as it annoys me every time someone says you should eat more as a blanket piece of advice to everyone, because I don't intuitively believe it, so want to read the evidence!!
The minimum number of calories that it's safe to eat isn't exactly the same for everyone, but I think 1200 is a reasonably good estimate for most people. 1000 might be ok for some people, but I think 800 would be too little for almost everyone.
It also depends on how good your diet is. If 300 of the 1200 calories are junk food, then you're probably not getting enough nutrients.
One way to know that you're not getting enough calories would be if you're hungry all the time, if you're often tired, or if you have trouble concentrating.
I am interested too and, honestly, do not know but I am finding that it is VERY hard to hit RDA minimums at under about 1100 calories. Now. How were those minimums established? I do not know. Because they are for raw micro-nutrients which are absorbed differently from different foods.
Frankly, there's not a lot of scientific evidence either way yet. A lot of it is professional educated guesses using information about biology and nutritional guidelines.
But if it helps, a few official health groups say 1,000 - 1,200 are safe, low calorie amounts for most women. Here are links:
An LCD limits calories, but not as much as a VLCD. A typical LCD may provide
1,000–1,200 calories/day for a woman
1,200–1,600 calories/day for a man
And I second what some others were saying - focus on a variety of whole foods to get maximum nutrition and limit junk food treats, and pay attention to signs of malnutrition. But that's just good advice for ANY diet, really.
Last edited by Chanticleer; 03-05-2018 at 10:57 AM.
Thanks Chanticleer that's great Some good info there and a good site.
As you say there are plenty of places giving guidelines that seem to agree in general - but it's not so clear on what evidence these guidelines are based.
After clicking through a few links of links from your links, Question 3 in this one at least gives evidence based 'state of the art' knowledge - but is still summarising what happens from a starting point of reducing your calories to around 1200 or other energy in/energy out options (and not exploring what happens outside these 'test conditions' of sensible measures). Still looks an interesting read. https://www.nhlbi.nih.gov/sites/defa...nce-review.pdf
But for example i don't think it covers the measurement of muscle-loss or any other of thos dire warnings of what is going to happen to you if you don't eat enough calories.
Actually, just thought, I should probably be sourcing the same sort of evidence-review publication from an anorexia angle instead of the obesity side....that would be a lot more focused on the consequences of too big an energy deficit (or defining a too big energy deficit)
Last edited by ange82much; 03-05-2018 at 04:29 PM.
Not eating enough calories won't immediately lead to muscle wasting if a) you have excess fat on your body, and b) you move around (or better yet, some exercise) - if you don't move at all, of course muscles will atrophy (like with someone who isn't mobile at all).
It's a common thing I've seen online that the thought is that if the body doesn't get enough calories, it bypasses the fat and eats up the muscle. This makes no sense for some basic reasons, including that fat is a big energy storage system (thus when you overeat the excess calories aren't stored as large amounts of muscle - I did not get ripped going to 215 lbs), and muscle is not the body's go-to for energy. Also, evolution-wise, it wouldn't make sense for the body to eat the muscle first, because muscle lets you move (gather food, avoid predators, care for offspring, etc.), and fat does not.
It would be different for someone who has classic anorexia, which includes a very low body weight. They don't have any extra fat (they don't even have enough essential fat), so their body would have to start breaking down other stuff.
It is normal to lose some lean mass when losing weight because the body doesn't need as much to move around because it's lighter. Unless someone works out specifically to maintain that lean mass from a higher weight (like the cutting that comes after bulking), it's not useful to the body, but it isn't used for energy before any fat is.
Last edited by Chanticleer; 03-05-2018 at 11:21 PM.
I like your thinking Chanticleer
So the conclusion i'm coming to (without having actually read anything lol) is that the 1200 calorie guidelines (and similar) are there because this is typically approx. a 500cal deficit and this is most likely to succeed as a long term strategy. Going with a lower number is probably absolutely fine (provided you get the right nutrients etc), but studies have shown that you're more likely to put the weight back on again with a more drastic weight-loss approach. Not sure where these muscle-loss stories are from then.
Last edited by ange82much; 03-05-2018 at 08:26 PM.
A lot of the starvation stuff came from the Minnesota Experiment-but these were men and not overweight to start with. I think there was some extrapolation from that for women....
Going with a lower number is probably absolutely fine (provided you get the right nutrients etc)
If you eat a perfectly balanced diet, and you're not hungry or tired, then yes, I think 1000 is probably ok.
If you're able to eat 1000 per day without being hungry, it could be because your metabolism is slow, which could be because you're not doing enough strength training. If you're not already doing strength training, then you'll probably make faster progress if you start strength training, even though you'll be eating more calories.
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Quote:
Originally Posted by mjf
If you eat a perfectly balanced diet, and you're not hungry or tired, then yes, I think 1000 is probably ok.
I agree with this. We are all different, so calorie requirements are different. It also depends on what you are eating. Foods that have a lot of fiber will make you feel fuller and therefore curb hunger more than those that do not and are usually lower in calorie. Our bodies also absorb nutrients differently. We need to make sure we are not eating the same thing every day. A wider variety of foods will make sure we are not missing any particular nutrients.
I think you would have to go for a very long time on a very low calorie diet before you will actually start to see evidence of nutrient shortage. Our bodies are made to adapt to different situations.
I am interested too and, honestly, do not know but I am finding that it is VERY hard to hit RDA minimums at under about 1100 calories. Now. How were those minimums established? I do not know. Because they are for raw micro-nutrients which are absorbed differently from different foods.
I did see a study once that said RDAs were determined eating 2000 calories. But, one thing your body needs nutrients for is digestion. So, if you are eating less... you need less nutrients.
A theory I heard one time, which to me makes sense, is that eating less than 1200 is dangerous because you don't have any fat on your body. But if you have fat, your body uses that for energy and thus.. it gets what it needs as if you were eating it.
But I believe that eating a low calorie amount CAN be dangerous for the simple reason that some people's bodies take action believing you are starving. I believe the body pulls back on thyroid hormone making you slightly hypothyroid which can't be good for you. It is remedied if you eat more for long enough to let your body accept you aren't starving.
interesting AnnRue, the news that if you eat less than 1200 means you're using your body fat instead of food for energy, since this is what we're trying to do! So that would suggest that it would be beneficial to be under 1200 during this process.... Would be nice to have the proper citation for that one as it sounds close to what's being mis-quoted elsewhere. Also for the thyroid thing.
On a separate note, this article is slightly off topic but an easy read about what 'starvation mode is' and seems legit. (Another topic of mis-statements and confusion!!) https://www.healthline.com/nutrition...-mode#section4
Last edited by ange82much; 03-07-2018 at 04:46 PM.
1,200kcal as a lower caloric intake limit is based on the idea that it would be difficult to consume sufficient food variety to ensure good health long term - specifically in reference to phytonutrients from fruit & veg, as well as vitamins and minerals. That is to say, it wouldn't leave enough 'space' in the calorie allowance to eat enough healthy foods - it's just a theoretical limit, with few to no studies to back it up. There's also the consideration that unless you're a 4'8" 100lb 60yo woman, chances are that your TDEE is higher than 1,200, and most physicians wouldn't advocate for extreme calorie deficits (more than 20% under TDEE) without medical supervision.
It's not a magic number though, and most definitely doesn't guarantee that you'll be 'using up' your body fat. If you are burning more energy than you're taking in, then your body will find the energy elsewhere - namely, from itself. It can catabolise fat, muscle, connective tissue, organs - whatever it needs! Generally fat and muscle are preferentially broken down - eating sufficient protein and resistance training at least twice a week will help skew the ratio towards burning more fat rather than muscle. Your body doesn't generally start breaking down organs and such until starvation levels for extreme periods of time.
Very Low Calorie Diets (VLCD) are acceptable as a short term fat loss strategy with medical supervision, because it's SHORT TERM; ie. not enough time to suffer hugely negative effects from a lack of nutrients. Also in consideration is that VLCDs are typically used only in cases of obesity, in which case there is a gross assumption that the excess body weight will have stored an excess of some vits&minerals; and finally that any negative consequences from low nutrients would be counter balanced by losing the extra fat, which comes with it's own set of health concerns.
For the record, going lower in kcal intake will not always result in more fat being lost/used - thermodynamics don't lie, and at the end of the day calories in/calories out is correct. HOWEVER, extreme caloric restriction comes with it's own fun set of different hormonal responses, which can in turn cause your body to BURN fewer calories - leaving you right back where you started, or worse. And while some of these effects can be reversed, for certain individuals it is permanent (adaptive thermogenesis, for example).
EDIT: If you're curious why people talk about lean body mass loss during caloric deficits for non-obese subjects, this study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970209/ has some interesting references in it. It's a generally accepted precept that the fatter you are (eg. obese) the more fat you'll lose proportionally to fat free mass. Conversely, the leaner you are (eg. normal, or even anorexic) the more fat free mass (usually mostly muscle) you'll lose in proportion to fat loss. For for example, a woman at 35%BF may lose 50lbs, 12.5lbs/25% of which will likely be lean body mass. However, if that same woman wanted to continue losing weight once she's 20%BF, it's more likely to be a 60% fat/40% muscle loss - with normal protein intake and no training. However, should this same woman eat at least 2.2-3.3g of protein / kg of bodyweight while trying to lose fat, and incorporated weight lifting 2-3x a week, it can help conserve LBM and preferentially burn fat. And yes, there are LOADS of studies that support this bit.
Scientific Papers on Minimum Calorie Advice
Some good info there and a good site.
