Sunday, August 16, 2009

Questions & Answers

Another Q&A. Click here to see all Q&A's.

Intermittent Fasting and Testosterone

First a question related to the effects of dieting on testosterone and libido/reproductive function in general -

Q: "My sex drive just winds down to nearly nothing when I'm running an intense caloric deficit. Is there some documented/anecdotal correlation on this, or is it random according to the individual?"

A: It's not random, it's a fact that weight loss/calorie restriction, even moderate in nature, causes a delayed response to gonadotropin-releasing hormone (GnRH). This neurohormone is secreted in a pulsatile manner from the hypothalamus, and upon binding to receptors in the pituitary gland, it activates synthesis of reproductive hormones, luteinizing hormone (LH) and follicle-stimulating hormone(FSH). This axis is partially under control by "master" hormones involved in sensing the general energy status of the body; leptin and insulin, for example.

An energy deficit lowers leptin, which in turn impacts the reproductive axis negatively. This makes complete evolutionary sense, when you consider that reproduction is such an energy costly process. Conversely, high body fat percentage also affects the reproductive axis negatively, through other mechanisms -insulin resistance being one major cause discussed in this context.

Looking at studies on this topic, the effect is proportional to the energy deficit. In one paper, they noted that the delayed response in GnRH pulsatility was "intermediate in extent" when comparing moderate weight loss (-1% body weight/week or some such) to that of anorectics or VLCD (400-800 kcal/day).

My personal experience is that a moderate deficit (i.e net deficit/week is moderate, say -3500 kcal) has no noticeable impact, while a high deficit (i.e -7000 kcal/week) has a negative impact. The latter is augmented on very low carb or straight ketogenic diets. Cyclical diets are superior in this regard.

And related to intermittent fasting -

Q: "I also have a question for you, regarding IF and testosterone. I found a study(done in rats,yeah) , which states that the IF mice had a much higher Testosterone to Estrogen ratio; one of the comments of the study "makers" was that in response to absence of food, males increase their testosterone in order to reproduce quickly as possible. Ok , it's very nice , but does this apply on humans? I mean are there any studies which concluded that IF raises testosterone in human males?"

A: Humans and rodents are not alike when it comes to the effects of fasting on the reproductive axis. For example, you'll see similar responses in female rodents becoming "hypermasculinized" when put on a 40% calorie restricted diet, which is obviously not the case with humans.

There's not a whole lot of studies that can be rightfully applied to the intermittent fasting protocol I am advocating, with 16 hrs of fasting and 8 hrs of feeding. The ones that come closest would be the Ramadan studies, which show a shift of the peak and nadir, but no reduction of the mean. Bascially, testosterone reaches it's peaks and low points at different times compared to a regular feeding schedule, but there is no impact on the average levels. Testosterone in blood plasma divided by 24 (hours) on Ramadan equals baseline (pre-study) levels.

Most studies in this context are carried out using prolonged fasting (48-72 hrs) and show a significant decline at the 36-48 hr mark. For example, one study fasted men for 56 hours, compared blood tests of the last 24 hrs and found lower levels compared to baseline. Other studies using similar setups found the same results (of note is that age plays a factor, and men 50 yrs+ seemed immune to these effects). Additionally, leptin replacement during prolonged fasting restores LH pulsatility and testosterone levels, which goes to show that plummeting leptin levels during prolonged fasting is responsible for the negative effect.

In summary, there is no evidence that short term fasting, which is what I recommend, impacts negatively on testosterone. Prolonged fasting has a negative impact, and this is related to the acute energy deficit and concomitant drop in leptin.

Here I go off on a tangent or two -

Speculatively, I suspect that the intermittent fasting protocol a la Leangains might alter the rhythm of testosterone and LH pulsatility in a similar manner as Ramadan, meaning your peaks would be different from that of the habitual breakfast eater. Ghrelin, which is also a key player in the reproductive axis, adapts to your habitual eating pattern and is altered compared to a more regular feeding schedule. High levels (such as in anticipation of a meal) inhibit GnRH secretion while low levels (such as after meals) stimulate it. Simply put, you may get hornier later in the day, although I've heard many anecdotal reports suggesting the opposite. Needless to say, there are many other, environmental factors that come into play here.

Also, recall that I always put the overfeeding phase post-workout. This will put your body in an acute positive energy balance and increase leptin; downstream effects of leptin will impact positvely on GnRH and testosterone, and provide a favorable hormonal environment for protein synthesis and anabolism. These effects would be especially welcome during a diet and perhaps one reason why intermittent fasting, according to my experiences, have shown such a remarkable effect on muscle and strength preservation during dieting. Admittingly, there are too many confounders here for me to make any definitive statements on the matter (is it the training, the diet etc).

Will aspartame kill me?

Q: "I was just wondering what your thoughts were on the use of artificial sweeteners (aspartame in particular). I love using them but have heard mixed advice regarding their safety. Some "experts" say they're fine in moderation, others say they can cause brain tumors and should be avoided like the plague. As in my eyes, you seem to be the one true "expert" on diet/training, your opinion would be greatly appreciated. Many thanks"

A: Aspartame was found to cause brain cancer in rodents, but no human trial has ever shown a link to cancer, or any other serious disease, for that matter. This has been examined extensively; for example, see this study with almost half a million subjects -

And here's another one -

I could go on, but the consenus is that aspartame is very safe for human consumption, and I have nothing against it.

Also, I should note that the rodent studies used such extreme dosages that it would be impossible for any human to ingest that amount save from walking around with an IV-drip of pure aspartame 24/7.

Transferring from dieting to maintenance

Q: This client had been dieting for several months and lost close to 25 lbs. It was time for transfering him to a maintenance protocol, which meant increased calorie intake. This is some of the advice I gave him.

A: As for your diet, I really recommend sticking to the same foods, or at least the same food types (lots of veggies, lean protein, no shakes etc) but in greater quantities for the first few weeks coming off the diet - trust me on this. Don't try adding in too much of anything funny like cheesecake or icecream or even cereal in your pwo meal. You WILL have a more lax attitude after this diet, and if you combine that with some really tempting foods, you'll risk a binge sooner or later. And that's a sure fire way to pack on the fat again after this long diet stint. You'll see I've changed the meal plans as well, simply added more of the old foods. Not that you need to use them either, but it's just to give you an idea.

He wrote back: "...make sense and I appreciate your advice to not deviate greatly from the food choices I made during the diet phase. It's good I enjoy those foods, so keeping them in my diet isn't an issue. With the added carbs, I'm going to take advantage and add more fruits and vegetables into my diet."

Furthering my point, I replied: Yes, that's perfect. More veggies and fruit. Changing food sources for novelty after a diet is one of the prime mistakes people make (but you don't hear people discussing this very much). It's a psych phenomenon, as deviating from their typical foods will put the majority in a more lax/liberal state of mind, esp after long bouts of dieting, which greatly increases the risk of going 'fuck this, this was so good that I'm gonna stop counting for today and just have a little bit more' and they then end up eating boxes of cereal and other high carb dense foods in the pwo meal.

Intermittent fasting and genotype

these questions comes up from time to time -

Q: "...would IF work for an endomorph?"

"Is there a particular genotype that seems especially suited to an IF eating pattern?"

A: The notion of people being born with a certain body type, somatotyping, has been around for ages. Though oversimplified, the idea holds some truth in that levels of hormones and neurochemistry are largely determined by genetics and gives a propensity for fatness, leanness and muscularity. The endomorph is basically a person that puts on body fat easily, also called the "thrifty" genotype, and the ectomorph, "spendthrift" genotype, is the person that seems to stay naturally thin and has a hard time gaining weight. Mesomorphs are muscular.

Part of the reason for endo/ectomorphism can be explained by the response to calorie intake. In short, ectomorphs match calorie expenditure to intake very well, and spontaneously; when overfed, they increase activity levels spontaneously (fidgeting, can't sit still etc) to burn off the excess calories, while this response is not seen in endomorphs. Overfeeding is also accompanied by an increase in resting energy expenditure in ectomorphs, while the effect is blunted in endomorphs. These are factors we cannot affect by dietary manipulation.

However, this is the interesting part.

Brain imaging reveals defects in the reward system of endomorphs, in that they have a poor concentration of dopamine (D2) receptors in an area of the brain that controls food intake. Dopamine is releases in response to pleasurable activities, such as eating, and is partly responsible for getting that satisifed feeling after a meal. If receptor density is low, more calories need to be ingested in order to reach that threshold - and endomorphs are screwed in this regard, in that they need larger meals than others to receive the same effect. The D2 dysfunction is one of the key genetical factors in causing obesity, and various D2 agonists are currently being proposed as possible drugs of choice to "cure" the obesity epidemic. Additionaly, D2 receptor dysfunction also predisposes individuals for various other addictive behaviors linked to the reward system (drugs, gambling, sex etc).

But let me get to the point. If there is a certain threshold of dopamine to be reached before feeling satisfied, and seeing that this response is blunted in endomorphs due to low receptor density, an intermittent feeding pattern would make a lot of sense for the endomorph trying to lose fat. Fewer and bigger meals would achieve the effect, while small meals throughout the day would just be half-assing it and never really deriving any pleasure from the food. The meals would be rewarding, and this brings me to the second argument for an IF meal pattern for endomorphs, which is the anticipation of reward.

Anticipation of reward has a very potent effect on dopamine levels. Think of how happy you were just hours before waiting to see an eagerly anticipated movie or going to an event you had planned for ages, only to find out that the movie/event itself was relatively disappointing (vs expectations). Parties, sex, food, gambling. Great excitement beforehand, yet often out of proportion to the feelings derived from the event itself.

Relating to the context discussed, the mere anticipation of the first meal after the fast, which is large and satisfying, may via increased dopamine have a suppressive effect on appetite. It may also improve other behaviors related to dopamine, such as sense of well being and motivation for work and achievement.

Therefore, endomorphs, and people with low basal dopamine levels (in psych referred to as "novely seeking" aka all-or-nothing personality types), may find themselves particularily suited to an intermittent fasting pattern. I should note that I am a legitimate novely seeker myself, as confirmed by rather extensive tests (long form Temperament and Character Inventory, for those in the know). Anecdotal reports from succesful clients also seem to suggest they may be of this temperament.

That being said, the above is a mere hypothesis at this point, and I am not really doing it justice by presenting it in a few lines in a Q&A post like this. More elaborate and referenced writings on this will likely appear in the book.

Extreme dieting, yet no fat loss?

Q: Recently, I got contacted by an old client of mine. He got very lean after his diet, but attending a few festivals during the summer got him out of his normal rut, and upon returning home he binged on junk foods for a few days. Eager to get back to his former leanness, he embarked on an extremely restrictive diet combined with copious amounts of cardio. Despite this rigorous regimen, appearance or scale weight didn't change much at all. He sought out my guidance again, and here are some excerpts from the conversation.

A: Yes, this is hardly surprising. You should have known better, but the correlation between prior dieting experience and rational behavior at times seem surprisingly weak. Even the best tend to do stupid shit from time to time.* As I've told you before, one of my friends is a coach himself, yet always hires another coach when he embarks on a pre-contest diet. Why? Most people tend to lose their objectivity and do stupid shit when left to their own devices. I used to do stuff I never would have advised anyone else to do, and it took several years before I finally learned.

It's the dumbbass diet you decided to put yourself on that causes the water retention. Extremely low calorie intake and HIIT cardio is a fantastic recipe for chronically elevated cortisol levels, which in turn causes water retention. If you've seen someone undergoing hydrocortisone treatment you'll know what I mean. The diet you're on now isn't much different, except the effects are more systemic rather than localized to certain tissues.

And then I told him my secret solution, which was basically to cut cardio substantially, along with a slight increase in calories, namely carbs pre- and post-workout.

The take away point here is this. Scenarios like the above, seems to happen a lot - people get lean, they binge, get some temporary bloatedness and they compensate by doing stupid shit against their better judgement. This will just aggravate the problem Fix your head and look at what the hell you are doing. A 1200 kcal/day no carb-no fat diet might sound like a good solution when your head is all messed up and you want to get rid of the bloat, but just wait it out and you'll see that it isn't as bad as you thought.

I should mention that cardio is the real killer here, not low calories per se. High frequency HIIT causes water retention due to cortisol. Long duration cardio, such as jogging for an hour or more daily, will cause it by an adaptive mechanism called hyperhydration. Competitive long distance runners and triathletes are keenly familiar with this, as they will sometimes lose weight after an event rather than when preparing for it.

Low calorie intake by itself is fine, but bad stuff happens when you add lots of cardio to the equation. And besides water retention, there's the more obvious drawbacks such as lethargy and general feelings of shittiness to cope with.

* In Fooled by Randomness, highly recommended, the author notes that researchers are overrepresented in failing to learn from past mistakes. In the same vein, I've noticed that theoretical knowledge about nutrition and training rarely show a strong correlation to good results among health and fitness minded people.


UofMWolverine81 said...


I've actually found it increasingly difficult to design my own training programs as my knowledge has expanded over the years.

When I started out, I trained intensely and tried to use some common sense and what I considered to be solid technique, but there certainly was little "elegance" to my program design. This approach, while hardly revolutionary, yielded excellent results.

As my knowledge grew, I found that programs for my clients were producing better and better results, and yet I still had a bad tendency to over-analyze and micromanage my own training. This left me longing to return to that original feel, but it's as if there was no off switch on my brain.

Due to this I am thinking about finally using some sense and "outsourcing" my own program design to a solid coach.

So I can empathize with that last point you made in this Q and A. Even recognizing that I should "know better" doesn't always seem to give me the needed kick in the pants to take action and promote positive change.

Anonymous said...

Great post as usual. Lots of original and thought provoking ideas.

Martin Berkhan said...


yes, I can relate. Not so much nowadays, but that was me a few years ago. There is this lingering notion that tried and proven approaches aren't adequate, and that you can improve, or create anew, an already successful concept (and that is usually a sure-fire recipe for failure).

Stefan said...

Like wolverine that last point really jumped out at me.
I have training ADD in that after a couple weeks on any program I feel there's improvements to be made, of course by jumping around from program to program i get nowhere and despite knowing this it still happens time and time again.

Also, just adding that the part on dopamine was interesting. Good stuff as usual

Martin Berkhan said...

Indeed. Training ADD is the scourge of many successful coaches. They can't seem to stick for a program themselves, yet preach consistency and slow progress to others. Their coaching may be top notch, but their behavior irrational, impulsive or in the worst case destructive. I've seen oh so many examples of this.

Chris said...

I'm ashamed to say I consider myself another coach that sometimes do not act in accordance to his knowledge.

Excellent post, Martin.

- Chris

Anonymous said...

I haven't read 'Fooled by Randomness' but 'The Black Swan' also by Taleb is excellent.

Applied to training, would you agree that some days should be 'heavy', some 'medium' and some 'light'?
i.e. you should wave the load.


BIGRED said...

I had a question regarding the Hiit + low calorie diets being a recipe for elevated cortisol and water retention. would this be applicable as well even if someone was not on a reduce calorie diet? or is just a byproduct of the combination of low calories and hiit? afterall athletes from all sports engage in various forms of high intensity + high volumes of traning, and many have great physiques and are not walking around bloated all the time. The difference being they are eating sufficiant calories. Would this be a correct statement?

Martin Berkhan said...

'Applied to training, would you agree that some days should be 'heavy', some 'medium' and some 'light'?'

If you're hitting lifts/muscle groups several times a week, intensity should generally be cycled, yes. This becomes more important as training experience increases - which I in the past learned the hard way. A beginner might find he can get away with 3x full body sessions/week, basically going 100% each session, not so with the advanced.

'The difference being they are eating sufficiant calories. Would this be a correct statement?'

Correct. Also, consider that athletes gradually ramp up volume and build up tolerance over years, which is hardly comparable to this case.

Anonymous said...

Great article again. I have one question. Have u ever tried the Scott Abel approach to your approach? like dieting with the same calories every day unntil you hit a point (fat % or other) that u can get a high calorie eat what ever u want day? ive read and spoken alot to his clients and they eat like crazy on these days and still they are at very very low bf%. Scott also proves with his research that this is good for you where he talks about leptin etc etc. Care to share some thoughts?

Martin Berkhan said...

No. What is the "Scott Abel approach to my approach"?

Wilmar said...

wow dude. droppin knowledge. word.

Anonymous said...

eating the same calorie amount consistent every day, regardless of how much you train each day. And when youre lean enough of other responses to your body that says that you need a refeed, u get one day or maybe a spike in the midweek aswell. But the one whole day is that u can eat whatever u like and how much you like. People eat like 10 000+ calories +. Its not about stuffing yourself that you want to phewk, but your just that hungry. There are of course studies left and right saying different things, but his argument is that calorie deflict is linked to longevity etc etc and other stuff. But if you have it for to long, your body will start to starve and reset your metabolic setpoint so that when you eventually overeat you will get fatter then when u started the diet. And your setpiont weight will be a litle higher.

mike said...

do a super cheat day in 2 weeks and you will reset at your leptins, and other hormonal s things and thats all.
A lot of sports&nutritional recommend to do a cheat day between 1-4 times in a month, especially if you are extreme lean
At least for me, i can loss fat while having 1 cheat day per week but its reduce the fat i have burned in the week so now i prefer to do 1 cheat day in 2 weeks.
Just like i will do this week because its my birthday so i will eat massive food :p

Martin Berkhan said...

I know from experience that such an approach, six days of dieting then eating as much as you can for a day, is counterproductive and dumb.

Yes, you'll bump up leptin, but it returns to baseline within days, and the negative effect of such gluttony is miniscule compared to the fact that you ate a bunch of shit, put on fat, took many steps back in your progress and now need to deprive yourself severly for several days to make up for the behavior.

It's also a sure fire way to develop an eating disorder that has much in common with bulimia. Look at these people in the off season, Most look subpar and it's not far fetched to claim that their all-or-nothing-attitude has something to do with this.

That being said, some get away with it - most notably, doped up bodybuilders and figure competitors. Or the rare individual that is able to take a moderate approach and knows that he's supposed to stop eating when he's feeling full (many people that engage in the shall we call it "Scott Abel" approach seem to lack this quality, believe me I know and I've been there).

So, I guess in summary, I guess what I'm saying is that I think the approach is fucking dumb, basically.

However, a structured refeed, popularized by Lyle McDonald among others, is another thing. The overfeeding phase I am referring to as part of my method is also similar in that regard, meaning it has rules and is not a free-for-all. This way you can flip the positives (leptin, glycogen replenishment, anabolism) in your favor, without the negatives and without having to starve yourself for the rest of the week, just so you can eat yourself silly and feel like shit for a day.

Chris said...

Well said. I agree completely.

Guys, go read Ultimate Diet 2.0. There's a review on this blog I think. Leptin and setpoint is explained very clearly in that book. I somehow doubt mr Abel has a very strong grasp on the concept.

- Chris

Anonymous said...

yeah good post,, i know bbers who diet with weekly cheats and we're talking like 10k calories a day cheats...they always seem to blow up in a bad way come off there might be something to it

morten_g said...

Speaking of scientists... you should see this particular comic strip:

rekrul said...

Martin, I know that you primarily dealt with the subject of the safety of aspartame in this post, but I came across a report concerning sucralose (Splenda)via GlobeNewswire that states:

"Among the results in the study by Drs. Mohamed B. Abou-Donia, Eman M. El-Masry, Ali A. Abdel-Rahman, Roger E. McLendon and Susan S. Schiffman is evidence that, in the animals studied, Splenda reduces the amount of good bacteria in the intestines by 50%, increases the pH level in the intestines, contributes to increases in body weight and affects the P-glycoprotein (P-gp) in the body in such a way that crucial health-related drugs could be rejected."

The source is a 2008 study that can be found here:

I'm not the best at translating these abstracts, and was wondering what your thoughts were.

They didn't appear to be using extreme dosages in this study. They were less than what's recommended for daily human consumption if I understood it correctly.

I do realize that I could just choose not to use the product if I'm worried about it, but I'd like to understand things in context, if possible, rather than be purely reactionary.


Anonymous said...


In response to the sucralose article, my bet is that if they took away the sucralose and administered the straight-up maltodextrin/glucose combination (which is what splenda is) they'd see the same results. I doubt sucralose by itself taken at "normal" dosages would see any of these effects.

Anonymous said...

Hello Martin, I hope you can answer my question.

I was reading through the Question and Answers and my attention was caught by "Extreme dieting, yet no fat loss?"
Ive been doing 1 hour long cardio everyday for a couple of months now together with 3 hour weight lifting a week. I also "lowered" my diet. Im a 17 year old guy with 16% but I want to get to 9-10%bf, but these extra fat doesnt seem to come off! So I tend to feel very demotivated because I see no rewarding results. I cant help to think that those 7 hours of cardio a week will do it. Im not desperate but I hope you could tell me what my workout should be. And dont get me wrong, Im not of those who ask before doing some research, its just that I believe Ill get the correct answer from you. Thanks. Im also thinking of doing Eat Stop Eat, I have no problem with fasting.

Well, Im looking forward for your response.

Greetings from Peru.

My name is Martin Berkhan and I work as a nutritional consultant, magazine writer and personal trainer.

Welcome to the Internet's leading resource on intermittent fasting and all things related.

FeedBurner FeedCount

Google Friend Connect

Join Me on Twitter


Follow Me on Facebook

Recommended Reading

Lame Title, Good Book

Recommended Reading

Intermittent Fasting for Fat Loss

Recommended Reading

Covers All Bases

Recommended Reading

Awesome Recipes for The Paleo Diet
Recipes for the Paleo Diet - Two Cookbooks - 120 Recipes Each!>

Recommended Reading

Fat Loss Made Easy

Great Interval Timer

+1 If You Think Leangains is Awesome