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Pros and Cons of Three Sizes of Calorie Deficits

Ignoring those people who deny the energy balance equation or even the concept of calories, the fact is that losing fat requires a calorie deficit.   But that raises questions of how to set the deficit (i.e. exercise vs. diet vs. a combination) or even the size of the deficit. Today I’m going to focus on the latter and examine the pros and cons of different size calorie deficits.

To keep the article from getting too complicated and long I am going to assume for simplicities sake that whether or not the deficit is created via dietary restriction or exercise the end result is basically the same. Please note that this really isn’t a safe assumption.  There are differences but those have to wait for another article.

Defining Different Sizes of Calorie Deficits

For the sake of this argument, I’m going to define the deficits as follows:

  • Small: 10-15% below maintenance
  • Moderate: 20-25% below maintenance
  • Large: anything bigger than 25% below maintenance

Note, I’m not saying that these definitions are the exactly right ones, they are simply how I define the terms.  As is usually the case you can find people arguing adamantly that only one or the other is appropriate.  As usual I take a little bit different view: each approach can be relatively more or less appropriate for a given situation.

As I examine each, simply for the sake of putting some real world numbers to what I’m talking about, I’m going to use two sample dieters both of whom have an estimated maintenance level of 15 cal/lb or 33 cal/kg.

  1. The first is a relatively ‘average’ female who weighs 130 lbs and has a maintenance caloric expenditure of 1950 calories per day.  Let’s just call it 2000 calories/day.
  2. 2 Our male weighs 180 lbs with a maintenance caloric expenditure of 2700 calories/day.Finally, I’m going to estimate weekly fat loss for each of the deficits as I go through.

I’ll use the standard estimate of a 3500 calorie deficit equaling one pound of fat loss and further assume that they lose 100% fat.   This may not be entirely accurate but will be close enough to make the point I want to make.

Small Calorie Deficit Diets

It’s not unheard of to hear of athletes or bodybuilders using very small calorie deficits to generate fat loss with a 10-15% deficit below maintenance being used.  As well, some diet experts tend to recommend small deficits for even the general dieting public.  Before looking at the pros and cons, let’s look at how this deficit will end up impacting on caloric intake as well as estimated weekly fat loss.

Estimated Fat Loss Small Calorie Deficit

You can see in both cases that the weekly fat loss is only moderate, as would be expected for such a small calorie deficit.  Importantly, notice that the male loses more fat at the same percentage deficit simply by dint of being larger.  As I discuss in detail in The Women’s Book, this one fact explains a great deal of why women lose less total weight/fat and lose it more slowly than men.  At the same relative deficit, their absolute deficit is smaller.

This was actually one of the reasons that I argue for using percentage based deficits in my first book The Ketogenic Diet, they take into account the individual needs of the diet.  That’s compared to either giving people absolute caloric recommendations or telling people to reduce their calories by some fixed amount.

Pros of the Small Calorie Deficit

First, some of the pros of this approach.  Clearly the deficit is fairly small and can be achieved relatively easily.  A small food restriction will usually accomplish it and often times, the deficit can be achieved by making simple qualitative changes in the diet (e.g. replacing 2% milk with fat free milk may save 40 calories and across three meals that’s 120 calories).

Even if absolute food intake has to be restricted, the difference is relatively small compared to normal eating patterns. For some people, this is beneficial behaviorally since they tend to do better with small non-intrusive changes.

It’s also often argued that this type of tiny deficit will have less of an impact on some of the counter-regulatory responses, the metabolic slowdown and such that can occur.  There is arguably some truth to this although the compromise for this is much slower fat loss (discussed next).  And, no matter what is done, eventually the body will adapt.

Finally, related to the fact that the adjustments are often small, it is often argued that long-term adherence may be better than more extreme diets; since there is less overall restriction involved in the first place, the odds of the person slipping or losing control is lower.  Again, there is some truth to this.

For performance type athletes, since there is never much extreme dietary restriction, the odds of hurting training or performance are lowered.  Big deficits can destroy training or at least require that it be modified to avoid the person crashing hard.  Small deficits generally avoid that.

Cons of a Small Calorie Deficit

But what about the cons?  The biggest issue with this approach is that the fat loss is so exceedingly slow.  Typically when I have seen people use this approach it is with folks who are relatively lean and don’t have much fat to lose in the first place.

A contest dieter (bodybuilder or figure person) who is starting close to their goal may only need to drop 10 pounds of fat to get into shape.  Of course, for our female, that still may require 20 weeks of straight dieting.  But for some people, and this is usually with folks who really know their bodies, this may work better.

For larger individuals, even with the relatively faster rates of fat loss, the slow rate of loss may be discouraging and frustrating.  As I discussed in another context in The Full Diet Break, individuals who have 50-100 or more pounds to lose often have a great deal of psychological struggle to overcome; losing a mere 1-2 pounds per week can make the diet take forever and that can lead to failure.

A final con is that this approach to fat loss is very easy to screw up.  With such a small deficit, the smallest mis-measurement of your food intake can eliminate the deficit entirely.   Again, in my experience the people who make this approach work are absolutely meticulous with their diet, they measure everything to the gram.  Otherwise, it’s altogether too easy for what you though was a 300 cal/day deficit to be nothing but a 100 cal/day deficit and fat loss slows to a crawl.

For the most part, I think the small deficit approach is best for the type of dieter I’ve described a couple times above: advanced dieters and/or athletes with relatively less fat to lose who are obsessively meticulous with their calories.  For others, a moderate or large deficit will probably be a better choice.

Moderate Calorie Deficit Diets

Next let’s look at moderate deficit dieting which is probably the most commonly advocated approach especially in the bodybuilding and athletic subculture.  As noted, I’ll be defining this as anywhere between 20-25% below maintenance calories.  Again, let’s look at what this makes the deficit and what the estimated weekly fat loss will be for our two sample dieters.

Estimated Fat Loss Moderate Calorie Deficit

Now we’re getting into more standard fat loss diets with recommendations of 1-1.5 pounds fat loss per week being a common recommendation.  Of course, the drawback is that a larger deficit must be created to get that level of fat loss.

Pros of the Moderate Calorie Deficit

Generally speaking moderate deficit diets tend to use a combination of food restriction and activity to accomplish the full deficit; I know I said I wouldn’t really talk about this in this article but it’s worth mentioning.  250-300 calories/day of activity with a 250-300 calorie/day food restriction is still pretty manageable and requires neither massive amounts of exercise or massive amounts of food restriction.  It is entirely possible to do the full deficit through food restriction of course.

This tends to allow much of the food flexibility and such that small deficit diets have as one of their pros; the diet only has to be changed minimally to achieve the necessary deficit.  Even there, moderate deficit dieting does feel like more of a diet than small deficit dieting, the individual will feel more restricted overall unless they create the entire deficit through activity.

For performance athletes, this is a benefit since it tends to have a small impact on gym or sports training.  This is especially true if concepts such as the refeeds and full diet breaks discussed on the site and in my A Guide to Flexible Dieting are adhered to.

Since the fat loss is faster, the diet tends to get finished quicker.  While some larger individuals with a lot of weight to lose may still find the prospect of dieting for a year to be overwhelming, at least things will be happening a lot more quickly than with small deficits.

In terms of screwing up, it certainly is possible to offset some of the deficit of a moderate fat loss diet with mis-measurement but it’s far harder to eliminate the deficit completely.  It can be done, make no mistake about it, but its relatively more difficult (what usually happens is that an expected 500 cal/day deficit ends up around 250-300 cal/day and people wonder why the fat loss is only half what it should be).

Cons of the Moderate Calorie Deficit

Metabolically, moderate deficit dieting does have an impact for reasons I’ve discussed endlessly on the site and in my books and won’t discuss again here. But between the rate of fat loss and impact of caloric restriction on hormones like leptin, etc. there’s no getting around the fact that the body will fight back to some degree with moderate deficit dieting (realistically: this will happen on any diet no matter what you do).

Frankly, outside of the fact that moderate deficit dieting may take really extended periods for very overfat individuals, I’d probably say it has the fewest overall cons relative to the potential pros.  Which is probably why it tends to be one of the most widely recommended and used approaches.

Of course, some people are still impatient and/or or have their own reasons for wanting or needing faster fat loss and the moderate fat loss of the moderate deficit can be both a pro and a con in that regard; it’s faster than small deficit dieting but under certain conditions may not be fast enough.

And that brings us to large deficit dieting.

Large Calorie Deficit Diets

Earlier in the article, I defined a large calorie deficit as 25% or greater.  However, just to illustrate the point, I’m going to use a massive 50% calorie deficit as an example.

I have actually advocated this size deficit in the first phase of my Ultimate Diet 2.0 but it’s also only for 4 days.  The Rapid Fat Loss Handbook actually revolves around protein intake rather than caloric intake per se but,on average, the deficit may end up at 50% below maintenance or even more.  So that’s why I’m going to use 50% for this illustration.

Estimated Fat Loss Large Calorie Deficit

You can see that at a 50% deficit, fat loss goes up significantly.  For the smaller woman it actually reaches the “ideal” 2 lbs/week the larger man achieves nearly 3 lbs/week.  For even larger individuals with a higher maintenance, a fat loss of 3-5 lbs/week or 1/2-2/3rds pound per day are not unheard of.

Pros of the Large Calorie Deficit

Now, clearly the biggest pro (to some) of this approach is that the rate of fat loss is maximal.  Even our smaller woman is losing a significant amount of fat per week and the male is dropping fat at a pretty absurd rate.   As noted, for bigger people, the numbers go up further and fat losses of 4-5 pounds per week are not unheard of.

Of course, a pro of that is the diet ends much more quickly than it otherwise would.  A diet that might have taken 2-3 months may be compressed into 4-6 weeks. For some people, this is a huge benefit as they can get back to serious training or what have you since the diet isn’t interrupting things for extended periods.

As well, in some situations (e.g. class reunion, wedding 2 weeks away), people may only have a limited time to lose the maximum weight/fat possible; that requires an extreme approach because there simply isn’t time to use anything slower.

For people with a large amount of weight to lose, seeing a quick initial drop can provide some nice positive reinforcement to continue with the diet.  Again, someone with 50-100 pounds to lose will likely be disappointed to drop only a pound or two in the first week.  A large deficit diet may generate a scale drop (and some of this is water weight) of 7-10 pounds in the first week.

This provides important immediate reward which may help some with long-term adherence.   Even a 2-4 week period with a large deficit to get some quick initial weight/fat loss before moving into a more moderate deficit approach can be beneficial here.

Assuming the diet is set up appropriately (primarily meaning it has sufficient protein) with the right kind of training, muscle loss should be nearly zero.  Certainly lean body mass may go down due to glycogen and water loss but it returns rapidly.

Certainly early research suggested that bigger deficits and very low caloric intakes led to more muscle loss but invariably they had inadequate protein and didn’t have weight training as part of the program.  When someone is on 300 cal/day and half of that is carbs, well, that’s only 40 grams of protein.  Of course muscle is lost, but not because calories are low per se; rather it’s because the diet is set up stupidly.

Cons of the Large Calorie Deficit

Which brings us to one of the cons: because of the massive deficit involved, most of it almost has to come from diet.  Most can’t spend the hours per day to expend the types of calories inherent to large deficit dieting so it comes down mostly to diet.

And since so few calories are being consumed, this allows for very little food flexibility.  My large deficit diets always end up being high-protein, low-carb and relatively low fat because that’s the only way to achieve the necessary deficit while providing sufficient protein.  There simply isn’t room for much else.

From a long-term adherence standpoint, that can be a problem.  Of course, my diets also always include free meals, refeeds and diet breaks to account for that but some can go crazy with such a limited number of foods available.

Then again, large deficit diets are rarely meant to be used in the long-term in the first place and often the short-period of extreme restriction seems to ‘reset’ some food issues for people.  They can lose their taste for a lot of the stuff that they used to over-eat previously and that can help in the long-term.

But what about adherence?  Once again, and contrary to popular belief, rapid weight and fat loss may actually be better for both short-term and long-term results than more moderate approaches.  But this is predicated on the diet being set up in a certain way.

The diet must change long-term food patterns (meaning it should revolve around whole foods, not protein shakes), it must include exercise, it must work on behavioral aspects of eating.  Not all large deficit diets are set up that way and the ones that aren’t are destined to fail.  Diets based around nothing but protein shakes shakes or that don’t include exercise never work.  They may generate amazing short-term results but nothing has been done to address long-term eating or activity patterns after the diet ends.

With a deficit that massive, it’s nearly impossible to completely offset the deficit without some pretty major screw ups in terms of food choices.  Make no mistake, it can happen, people end up choosing high-protein foods that contain too many tagalong fats and carbs and this offsets the deficit.  But even with that, the deficit ends up being pretty damn big and fat loss is pretty quick.

On that note, the severe restriction can be too much for people although, interestingly, many report that hunger actually isn’t a huge issue.  Between the hunger blunting effect of massive amounts of protein and other issues, hunger often goes away.   This isn’t universal but happens more than you might think.

As well, long-term adherence can be an issue and returning to maintenance caloric intakes is a problem for some. This is actually a big part of why large deficit diets are best set up around whole foods.  When the diet is based around protein shakes, the dieter has no idea how to ‘eat normally’ when the diet is over.

When the core of the diet is based around whole foods (e.g. lean protein, veggies, essential fats), the dieter simply adds other foods back to that core when the diet ends (or they choose to move to a more moderate deficit).  Even there, some people simply can’t make large deficit diets work, they end up yo-yoing back and forth and should consider something else.

Of course, metabolically, large deficit dieting can have the biggest impact on metabolic parameters.  But that’s the price to pay for faster rates of fat loss.  As I’m fond of saying, life she is full of these little compromises.  If you want to have a minimal impact on metabolic rate and such, use a smaller deficit; the price is simply slower fat loss and a longer diet.

Of course, properly scheduled refeeds and full diet breaks help to offset much of this so large deficit diets can still be made workable if you do it right.  Again, they still aren’t for everyone.

Finally, large deficit diets have the greatest impact on training and ability to train.  It actually turns out that too much activity with a large caloric deficit can cause more problems than it solves and, generally, training has to be massively curtailed during the diet.  For people who simply love training, or must train a lot for whatever reason, large deficit diets are unworkable.  They must do something else.

Then again, for some athletes, a 2 week block on a large deficit (with training severely cut back) can be used to let them get back to training and may have less of an impact on training than having to diet moderately for 10 straight week.  This simply depends on the specifics.

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25 thoughts on “Pros and Cons of Three Sizes of Calorie Deficits

  1. I usually put my clients on a larger deficit tword the beginning of their diet. Simply because we as humans want the quickest results possible. Once the water comes off and clients SEE results from the scale, they are more apt to stick with their large deficit diet. Until leptin and other hormonal factors become an issue its time to up the calories.

    Im currently on the frosted flakes diet: 4 cups a day at 110 calories per cup plus skim milk. BEST DIET EVER!!

  2. Great, nice easy read on the pros and cons of different approaches. I find giving my clients a choice has been working for me. Most start on the large deficit approach, but them move to the moderate deficit as they approach their goal weight. Also providing the opportunity for them to use training and/or diet to make up those deficits is a great idea. Some thrive on hard, regular training, and others have every excuse in the book not to attend training.
    The Pros and Cons are different for everyone.


  3. Sorry scot but the best type of eating its INTERMITENT FASTING, its the only diet that you can eat until you get ultra full, and be able to eat ice cream and others things that not another diet allow. never hungry, no ansiety, no nothing. just waiting to your eating window and eat a lot

  4. Mike: Best diet for what? Fat loss? IF for fat loss wont work if your still eating a surplus in calories.
    IF is more of a hunger controlling thing for me.

  5. I do not believe that there’s such thing as BEST in general sense. As much as I can see a lot of sense in IF I still think it all depends on criteria and individual factors. For centuries science seems to have been trying to mold public consciousness into a concept of absolute truth for everyone (in areas like exercise, nutrition, etc.) only to discover that there’s no “one size fits all” rule… that’s why I like Lyle’s approach of presenting facts without preaching any magic solutions… if it works well for someone – great – as long as we understand that same approach may not work equally well for others… just my two cents

  6. Scott – how are frostied flakes helping to control hunger or preserve LBM?

    I haven’t looked into Intermittent Fasting, but this sure does sound a lot like Bulemia?

    “…INTERMITENT FASTING, its the only diet that you can eat until you get ultra full, and be able to eat ice cream and others things that not another diet allow. never hungry, no ansiety, no nothing. just waiting to your eating window and eat a lot”

    Do you have any more information on IF, how it works and what results people typically get?

  7. I wonder when Lyle will weigh in with his take on IF. Alan Aragon already has
    It seems to work wonders for some.

  8. Sorry Lyle but what do you mean when you say large deficit diets greatly affect ‘metabolic parameters’, is this just hormones or is it more???

  9. I always get a chuckle when people get really dogmatic about some new type of diet or training approach. IF is fine….in fact, I follow some IF principles a few times a week, but to call it the “best type of eating” is missing the point.

  10. LG

    Who said anything about my frosted flakes diet controlling hunger and preserving LBM?

  11. It’s all about transitions. You go higher deficit at certain times, lower deficit at certain times. A diet can manipulate carbs and fat, but protein has to stay constant based on body size, mostly. You go lower carbs, lower fat at certain phases, then lower calories, depending on how the diet is affecting you (plus, an eye towards your current workout regime).

    People seem to want to do one thing or the other, but with tracking and a bit of ‘listening to your body’, transitioning from one ‘type’ of diet to another as you lose seems to work pretty well, at least for me. YMMV, FWIW, IMO.

  12. I’m with Tony K on that one. If I wake up and I’m not hungry, too busy, or just a little hungry I usually let it ride till I’ve been 14-16hr without food……Which is IF
    However, U do have to eat bigger meals on IF. Thats just the way it is. This can cause problems. It can make you sleepy bloated or just low on energy. For me it basically comes down to weather or not you like the feeling of fasting and then eating big meals or just snacking and having a more even energy level. Also……If you work out A LOT. Like hours of Martial Arts a day. IF can be tough. Sparring after a big meal doesn’t work well…..obviously. Sparring in a fasted state is great but……if you go for too long you might have a blood sugar crash. Which is also a problem. But I must say, most of the best martial artists spar on some kind of an empty stomach…..just eating small snacks to keep themselves going until a big meal when it’s all over.
    This is only from my experience with Krav Maga though. (But I have been doing it for a long time)
    Bottom line- digesting food takes energy and if you work out while your digesting a lot your workouts will suffer.

  13. So if someone is doing a small deficit of say 10-15%, and is below 10% body fat (cat 1 dieter), do they really need to be doing free meals and/or refeeds or this that meant for larger deficits?


  14. I ran Nutrisystem with a big emphasis on added-in veggies. (Heck I really learned how to cook from NS, was eating at restaruants very dinner before.) Had some decent exercise so that even at a bit over the recommended 1500 calories/day, I was still doing 1500 calories/day deficit. I think this was best for me. More motivating. And taught me good patterns. Went from 230 to 160 in 7 months.

    Never cheated though. Cheating is the killer. It’s not just the calories from the cheat but how it screws your willpower up for the long haul.

    P.s. I think the best way to “measure your deficit” is to look at your long term loss rate and impute the deficit from that. If you are doing consistent activities and a certain diet and have 3#/week loss rate, then you must mathematically have a 1500 calorie deficit. Forget figuring it out from the ground up. Just use what the loss rate implies.

  15. I also totally changed my eating pattern. Lots of minimeals. Lots of volume. Eat breakfast. Eat late (a salad before bed). Eat when not hungery (heresy!) But I found doing this totally pre-empted cheats. It really really did.

  16. Hi Lyle,

    Your articles are fantastic.
    However, I do have a question.
    I’ve read both here, and in one of your books (Rapid Fat Loss Handbook) that engaging in a lot of activity (mainly aerobic) while on a very low calorie diet can slow weight loss efforts?
    Why is this?
    If one has a high caloric deficit and then increases that with exercise, according to the energy balance equation wouldn’t that increase weight loss? I understand that with such a big deficit, the negative hormonal responses of your body are increased but you yourself have said that they’re not enough to eliminate the deficit completely.

    If you could clear this up for me it would be much appreciated!!

  17. At some later date I will explain what I think is hapepening in full. For now, simply take it at face value and/or MAGIC! But that’s what invariably happens.

  18. I have a question and I want to preface it with this: I AM NOT TRYING THIS,JUST CURIOUS

    Based on RAPID FATLOSS HANDBOOK, which I have read

    If a person takes a great full spectrum amino supplement would that allow for a human to reduce food calories and spare organ breakdown in the body? Essentailly seriously reducing calories with out reducing “the building blocks” and essential nutrients for survival?

  19. I suppose in premise this is possible (MAP anybody?) but I still don’t think it’s a good idea. Such a product wouldn’t do anything for fullness, satiety or long-term food habits which are just as important as anything that might be gained from it.

  20. Great article Lyle, very clear and lays out the behavioural aspects alongside the physiological. Interesting about the macro set-up for larger deficit diets being so poor. No wonder there was muscle loss.

  21. Great article, and one of many I’ve read tonight, but one thing I’m confused about is the largest deficit’s impact on metabolic parameters.

    Is this a permanent impact or something that irons itself out after a while?

    For example, if one lost 50lbs through 33%-50% deficit, would their metabolism be permanently lowered as opposed to a person who took longer to lose the same amount of weight via a 10% deficit?

    And by permanently lowered, I mean even if the weight were gained back, the metabolism would be permanently ‘damaged’.

  22. Hey Lyle,

    I recently graduated from university, and found in the last months leading up to my graduation, i significantly let myself down – i put on almost 8 kgs! 🙁
    I have been reading a lot of the articles you have posted and found myself a little relieved and a little perplexed.
    Having coming back home for a holiday, 1 month and a couple of days to be precise, I decided that with the availability of healthy food, a gym right around the corner, and my mom to help keep me on track, this might the perfect (and only) opportunity for me to drop those kgs, and fast.
    For about 1.5 weeks now, I have been trying to burn around 1000 calories minimum with a combination of cardio/weights per day, and i have cut out carbs from my diet almost completely, save for a spoon or two of rice or buckwheat pasta a day, so it is safe to say that my caloric intake would not be more than 1000 a day.
    Is what i am doing alright? Will I be able to drop the 6kgs by the time 3 weeks come to an end? I know its sounds rash, but after trying a gazillion types of workouts, this is my last resort, and quite frankly, my last hope.

    I really appreciate anything you have to say.
    Thanks in advance! 🙂

  23. I am seeking your advice as I find your informations so valuable however im unclear how to apply it to myself.
    I am a 33 yr old mum 72kg 30%BF 163cm . I am a habitual dieter whose diet has stalled for 6 months now. I wear a fitbit activity tracker and my average expenditure is 2500 cal a day and im eating 1600 and am not losing weight. I use a food scale and MFP. I do a cross fit style class twice a week ( HRM says 1000 calorie) and one full weights session a week ( 500 cal). I was also doing 1 hr brisk walks per day as well as training qat the gym but have stopped in an experiment to remove excessive cardio and focus on weights.
    I have had my RMR tested and it was 1440 cal at rest. I went to a dietician who told me just eat 1200 cal but I feel exhausted and Hangry when I do that.
    I have been focusing on increasing protein and watching my macros to find a balance 40/40/30
    my fitness has improved out of sight however I cannot seem lose weight and its driving me crazy and im not seeing any measurable fat loss. im frustrated as simple maths is not working for me
    what am I doing wrong?

    should a aim for a smaller deficit? take a diet break? ( insert crazy lady OMG weight gain gif)

    Im not looking for an easy solution . I understand body composition changes take time however I would expect to see progress after 6 months

    any guidance you could provide would be greatly appreciated

    thanks in advance

  24. Lyle, everyone always says diet slow and less aggressive because of metabolic adaptions and that the body will “get use to the lower intake” faster then if you were to cut slowly but wont the metabolism basically only adapt based on the reduction on body weight and that the adaptive component is just simply overblown and the main true reason why people shouldn’t cut aggressively is just because of the mental stress and higher possibility of loss of muscle. the arguments for adaptions happening really soon and basically cutting to aggressive and “running out of room to pull from much sooner then if dieted slower” since u started to aggressive and have now adapted is that argument just nonsense in your opinion because i hear mixed opinions everywhere and want to know your views on both points

    [WORDPRESS HASHCASH] The poster sent us ‘411571586 which is not a hashcash value.

  25. Read the article Is Rapid Fat Loss Right for You? I addressed the metabolic slowdown issue in this piece already.

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