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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.

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