A very interesting and informational read on deficits...

The New Rules of Cutting Calories: What is the "Real" Ideal Calorie Deficit?

By Tom Venuto

New Research and Insights on The Optimal Caloric Deficit For Fat Loss

How far should you cut your calories in order to lose fat safely at the optimal rate? How large of a deficit is necessary? What is the lowest safe level of caloric intake? Why do some people lose a lot of weight on very low calorie diets, apparently without problems? Should the calorie deficit be the same for everyone, or, like other aspects of nutrition, does the calorie deficit have to be individualized as well? Because these and similar questions continue to come up so often in a variety of scenarios and because recent research has shed some new light on the subject, this new article revisits "the optimal calorie deficit" including that old advice about "cut 500 calories a day to lose a pound per week, cut 1000 calories a day to lose two pounds per week... and much more.

3500 Calories - A Pound of Fat or Six Pounds of Muscle?

First, let's clear up something about the old standard advice: "There are 3,500 calories in a pound of fat, so to lose a pound a week, you need to cut your calories by 3,500 per week." Actually, it's not quite that simple.

New research has been published that we have frequently cited here in the Inner Circle, because it is the basis on which we have developed THE NEW BFFM CALORIE DEFICIT GUIDELINES. Dr. Kevin Hall, an investigator at the National Institute of Health, has focused his research on the various mechanisms that regulate human body weight and much of his work was based on the previous findings of fellow obesity researcher Gilbert Forbes. Hall recently published a new paper in the International Journal of Obesity that throws a wrench in the works of the "3500 calories to lose a pound" idea…

The equations in his paper were so complicated they made my head hurt, so I'll spare you the details, but despite all the math he used to draw his conclusions, his article clearly prompts an interesting question: "A 3500 calorie deficit to lose a pound of WHAT?"

Below, I've summarized Dr. Hall's research paper into a list of points that any non-scientist can understand. Read them carefully - they contain a lot of simple and practical tips you can use to properly balance your caloric intake with output, fine tune your calorie deficit and help you retain more muscle when you diet.

Research On The Calorie Deficit Says:


3500 calories to lose a pound has always been the rule of thumb. However, this 3500 calories figure goes back to older research which assumed that all the weight lost would be adipose tissue.
At least a small amount of lean body mass is almost always lost along with body fat, which would indicate that the 3500 calorie figure could be an oversimplification.
The amount of lean body mass lost is based on initial body fat level and the size/severity of the calorie deficit
Lean people tend to lose more lean body mass and retain more fat.
Fat people tend to lose more body fat and retain more lean tissue (revealing why obese people can tolerate aggressive low calorie diets better than already lean people)
Very aggressive calorie deficits and low calorie diets tend to erode lean body mass to a greater degree than more conservative diets.
whether the weight loss is lean or fat gives you the real answer of what is the required energy deficit per unit of weight loss
The metabolizable energy in fat is different than the metabolizable energy in muscle tissue. A pound of muscle is not 3500 calories. A pound of muscle yields about 600 calories.
If you lose lean body mass, then you will lose more body weight than if you lose fat.
If you create a 3500 calorie deficit in one week and you lose 100% body fat, you will lose one pound.
If you create a 3500 calorie weekly deficit and as a result of that deficit, lose 100% muscle, you would lose almost 6 pounds of body weight! (of course, if you somehow manage to lose 100% muscle, you will be forced to wear the Dieter's Dunce cap)
If you have a high initial body fat percentage, then you are going to lose more fat relative to lean, so you may need a larger deficit to lose the same amount of weight as compared to a lean person
Creating a calorie deficit once at the beginning of a diet and maintaining that same caloric intake for the duration of the diet after major weight loss fails to account for how your body decreases energy expenditure with reduced body weight
Weight loss typically slows down over time for a prescribed constant diet. This is either due to a decrease in metabolism, a relaxing of dietary compliance, or both (most people just can't hack aggressive calorie reductions for long).
Progressive resistance training and or high protein diets can modify the proportion of weight lost from body fat versus lean tissue (which is why weight training and sufficient protein while on calorie restricted diets are absolute musts!)
The NEW BFFM Calorie Deficit Guidelines

So, based on this new information, should we throw out our old caloric calculator forumulas? Well, not necessarily. You can still use the standard calorie formulas to figure out how much you should eat, and you can use a 500-1000 calorie per day deficit (below maintenance) as a guideline to figure where to set your calories to lose one or two pounds per week respectively. The math doesn't always come out in the real world the way you anticipated on paper, but the standard calorie calculator formulas are as good a place to start as any because you are going to adjust your calories weekly in real time anyway.

What we can do however, is to improve our calorie deficit guidelines using a sliding percentage scale of conservative, moderate and aggressive deficits, which you choose based on your starting body fat percentage. This gives you a much more personalized and effective approach than an "absolute" deficit like 1000 calories. In relative terms, a 1000 calorie deficit could be near starvation, or it could be a perfectly reasonable reduction.

For example, if you are a large and highly active male with a 3400 calorie per day maintenance level, then a 1000 calorie deficit means a daily caloric intake of 2400 calories per day, a 30% deficit (aggressive, but well within reason). If you are a petite, inactive female with a caloric maintenance level of 1900 calories per day, then a 1000 calorie deficit means a caloric intake of 900 calories per day, a 53% deficit (semi starvation, and potentially unhealthy). As Einstein would say, that's relativity for you.

The fix is simple, instead of using 500 or 1000 calorie per day deficits as fixed standards, use a percentage, and set up a sliding scale that accounts for your goals, your desired rate of rate of weight loss and your starting body fat percentage.

15-20% below maintenance calories = conservative deficit
20-25% below maintenance calories = moderate deficit
25-30% below maintenance calories = aggressive deficit
31-40% below maintenance calories = very aggressive deficit (risky)
50%+ below maintenance calories = semi starvation/starvation (potentially dangerous and unhealthy if not medically supervised)

Maximum Deficits (The Calorie Floor)

Previously when I've been asked what is the lowest you should go in your caloric intake, I've often given the absolute numbers 1200 calories for women and 1800 calories per day for men. These are pretty good guidelines that apply to most people most of the time, but not 100% of the people 100% of the time. If you're a large and highly active female with a total daily energy expenditure (TDEE) of 2600 calories per day, then 1200 calories would be a starvation level diet for you (54% deficit). Again, because of relative differences between genders and individuals, if you can customize, then do customize, instead of using absolutes.

So where did the 1200 and 1800 calorie floor numbers come from? Those are generalizations based on average caloric maintenance levels (TDEE), as determined by exercise physiologists. According to Victor Katch & Frank Mcardle, the average female between the ages of 23 and 50 has a maintenance level of about 2100 calories per day and the average male about 2800 calories per day.

Based on the maximum recommendation of two pounds of weight loss per week given by organizations like the American College of Sports Medicine, these "calorie floors" are based on 1000 calories below the average person's TDEE (2800 calories per day average for men, minus 1000 calories equals calorie floor of 1800 calories per day. 2100 calories per day average for women, minus 1000 calories equals a calorie floor of 1100 calories, and most health organizations round up that number to 1200 since 1000 calories under maintenance is a larger relative deficit compared to men.)

Differences in calorie deficits based on starting body fat

Usually, we would suggest starting with a conservative deficit of around 15-20% below maintenance. Based on the research, however, we see that there can be a big difference between lean and overweight people in how many calories they can or should cut.

If you have very high body fat to begin with, the typical rules of thumb for calorie deficits may underestimate the deficit you need to lose a pound. It may also be too conservative, and you can probably use a more aggressive deficit safely without as much worry about muscle loss or metabolic slowdown.

In fact, I've found that since overweight folks have higher calorie requirements than smaller folks, they often find that a small calorie deficit of 15-20% is still a lot of food and leaves them feeling pretty full! Not only is the 25-30% more effective in their situation, it's more practical too because the food quantity is more appropriate relative to their appetite.

If you are extremely lean, like a bodybuilder trying to get ready for competition, you would want to be very cautious about using aggressive calorie deficits. You'd be better off keeping the deficit conservative and starting your diet/cutting phase earlier to allow for a slow, but safe rate of fat loss, with maximum retention of muscle tissue.

Should You Be Aggressive or Conservative When Choosing a Calorie Deficit?

when deciding whether you should be more aggressive or more conservative with your deficit (15% vs 30% or even higher), I'd suggest four considerations:

1. Take into account your starting body fat. If you have high starting body fat, then you are at less risk of losing lean tissue because you have a large storage depot of energy (body fat), therefore reducing the body's starvation signals. If you have a low starting body fat (ie, bodybuilder or lean person trying to get even leaner), then you are at higher risk of losing lean tissue with an aggressive calorie deficit, especially with a high level of training volume and intensity.

2. Take into account your actual real world results. If you are losing fat and maintaining all your lean body mass on an aggressive deficit (30% or so), and you are not experiencing undue hunger, then why not stay with it? (You'll get maximum fat loss that way). If you're on a very conservative calorie deficit of 15% and the fat loss is painfully slow, then why not increase it a bit? (you'll speed up fat loss that way)

3. Use both sides of the energy balance equation. Could you leave your calories at a 20% deficit via reduction in food intake, but increase your activity to get the overall 30% deficit? Ie, does it fit your lifestyle and schedule to take a "higher energy flux" approach and simply get that extra calorie burn by exercising more rather than eating less? If so, then consider raising your calories burned rather than cutting your calories consumed.

4. Take into account your need to reach a deadline. When you think about deadlines, ask yourself whether you will accept higher risk (of muscle loss, etc) and the discomfort of more potential hunger, in order to reach a body fat goal on a specific target date. (But if you're rushed to make a deadline, just make sure it doesn't happen again. Learn from this first experience, plan better next time and start sooner so you don't have to crash diet to make your event on time).

What about medical weight loss and protein fasts?

Anyone who has ever been on a medically-supervised liquid weight loss diet or a self-administered protein sparing modified fast (PSMF) diet, may see a contradiction in our BFFM deficit guidelines. They might point out that their own medical doctor put them on 50% of their maintenance calories or even less (often only 800-900 calories per day - technically, a crash diet, right?) If it's bad for you to cut calories so much, then why would a doctor recommend it?

Well, keep in mind the context. In the cases of morbid obesity, a risk to benefit analysis has to be done. The risks of staying grossly overweight far exceed the potential downsides of an extremely low calorie diet, and the doctor knows that as sure as the sun will rise in the East tomorrow, the weight will come off fast with a large calorie deficit. In some cases, it's saved as a last resort. In other cases, a doctor will make a judgement call on whether to start someone on a liquid protein or PSMF diet. In all cases, the patient is under the doctor's supervision and ensures adequate nutritional intake using supplements.

What about the high risk of muscle loss? Is that ever worth it? Well, again consider the patient, the urgency of the need to lose weight and the starting body fat. As the research indicates, the highly overweight person is less likely to lose muscle with an aggressive deficit. Some of the weight lost is going to be muscle and other lean tissue, no doubt about it, but it will be less than a lean person and even if LBM is lost, again the benefits outweight the risks.

In the personal sector, we have commercial diet programs and very strict diet programs or mostly liquid protein "rapid weight loss" diets often recommended by trainers or bodybuilding and figure coaches, which also call for extreme calorie cutting. Unlike medical weight loss, this is generally a bad idea, because the bodybuilder or figure competitor is already lean. As the research shows, the lean person is far more likely to lose muscle with an aggressive calorie deficit, and even though high protein intake spares muscle, lean people need to be much more conservative with calorie cutting. A lean person wanting to get even leaner should start far enough out from their goal target date so they can lose at a rate of 1.0 to 1.5 lbs per week to maximize retention of lean muscle. In this scenario, the risks of large calorie deficits and fast weight losses outweight any benefits. At the very least, this approach needs to be called out for what it really is: Crash dieting and impatience.

In contrast to these extreme scenarios, the BFFM calorie deficit guidelines were written as Lifestyle Guidelines. No one should be dieting in a caloric deficit forever, so in that sense a calorie deficit is never a "lifestyle" unless you're into that calorie restriction for longevity stuff (and don't get me started on that one). However, the best method is to take a lifestyle approach during the fat loss phase, which simply means, avoid extreme dieting, take a more balanced approach, be patient and be pleased with slow but steady weekly fat loss.

Adjusting The Deficit In Real-Time

It's VERY important to understand that once you've done your initial calorie calculations, then after you start, you need to adjust your calories and your entire approach in general, according to your actual real world results. You should not try to re-calculate your calories every day or even every week using the formulas again.

Adjusting caloric intake (nutrition) and caloric expenditure (training) in real time is critical, because energy balance is dynamic. This means that the amount of calories you require today may not be the same three or six months from now. If your weight changes substantially, your calorie needs will change. If your activity level changes substantially, your calorie needs will change.

In general, as you lose weight, your calorie needs decrease because it takes fewer and fewer calories to move and maintain a smaller body. For example, after a typical 40 pound weight loss, you will need 300-350 fewer calories than when you started, if all else remains equal. Think about the implications of this! It means that your rate of weight loss will automatically decline by 2/3 of a pound per week if you fail to adjust your calories consumed (eat less) according to your new body size or increase your calories expended (burn more). Researchers call this "The energy gap" and it explains slow weight loss, it partially explains plateaus and it largely explains why it's hard to keep weight off after you lose it.

On the other hand, just because energy balance is dynamic doesn't mean you should crunch your numbers every day. You could drive yourself insane trying to re-calculate your calorie numbers and deficits every day. So don't try. Instead, do your calculations once at the beginning of your program. Follow your prescribed calorie level diligently for a week to establish a baseline. After that, adjust your approach (food intake/ exercise output) according to weekly real world results using the BFFM "Feedback Loop Method."

When To Re-Calculate Calories

There are three times when you may want to go back to the calorie calculators and re-calculate both your total daily energy expenditure and your optimal daily caloric intake to reach your goal.


1. Re-calculate calories each time you start an all new program/goal cycle
2. Re-calculate calories each time you've had a major change in body weight.
3. Re-calculate calories each time you have a major change in activity.

Also remember that it is a very good long term goal to reach a point called "unconscious competence" when you have gone through all the number crunching, calorie counting, journaling, tracking, measuring and so on, and after many months of this, it all becomes second nature. At that point you may not have to ever count or crunch numbers again. The analytical and detail oriented personality types will probably always want to run the numbers and print out menus with calories and macros, but at the point of unconscious competence, it becomes a choice and not a requirement.


The bottom line

When you are calculating your own deficit, be sure to take into account your starting body fat, your personal goals, the time available to reach your goal and be sure to weigh the risks and benefits of whatever approach you choose. Avoid getting locked into a single prescription for calorie deficits for weight loss. As you can see, one size does not fit all. If a highly conservative dietician for example tells you to choose a 15% deficit and you are 100 lbs over weight, it's entirely possible that this could be too much food for you and your weight loss would be unnecessarily slow. The recommendation was intended for your health and safety, but it could actually end up being a de-motivator.

Your optimal calorie deficit could be anywhere from 15-30% below maintenance and this is the offical Burn The Fat, Feed The Muscle program recommendation for fat loss. This is consistent with well-accepted weight loss guidelines from organizations like the American College of Sports Medicine and the American Dietetic Association. The new guidelines for adjusting the percentage deficit based on your starting body fat level are based on the research of Hall and Forbes. Put together, you now have the tools to customize your calories with the greatest precision possible.


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References:

1. Forbes GB. Body fat content influences the body composition response to nutrition and exercise. Ann NY Acad Sci. 904: 359-365. 2000
2. Hall, KD., What is the required energy deficit per unit of weight loss? Int J Obesity. 2007 Epub ahead of print
3. Hill, James, Understanding and Addressing the Epidemic of Obesity: An Energy Balance Perspective. Endocrine Reviews, 27: 750-761. 2006
4. McArdle WD. Exercise physiology: Energy, Nutrition, and Human performance. 4td ed. Williams & Wilkins. 1996
5. Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 6: 542-546.