While strength trainees often focus on their carbohydrate intake because, God forbid, if they have one low carb they they will be completely depleted and ''flat'' because of it, I often do not care about carbohydrates as much as I care about fat intake.
Even when I am setting up a diet for my clients, protein and fats are determined and optimized first, while carbohydrates are used to fill in the remaining caloric budget. There are 2 main reasons why you should care about your fat intake:
1. Increased anabolic hormone production
2. Anabolic effects of certain fatty acids.
As fat intake is directly related to anabolic hormone production such as testosterone, estrogen, growth hormone, and IGF-1, it becomes very important to optimize fat intake for maximum muscle growth.
Research shows a clear trend of an increase in testosterone in men and both testosterone and estrogen in women with higher intake of fats. The relationship with fat intake and anabolic hormones is correlated and it goes in both directions, meaning with low fat intakes, testosterone also decreases. This can have negative effects on muscle growth.
Goldin et al. (1994) did a study on women where they initially had a meal plan consisting of 40% fats. After switching to a lower fat level, which was 20-25%, there were significant decreases in serum concentrations of estrone, estrone sulfate, testosterone, androstenedione, and sex hormone binding globulin (SHBG) and near significant decreases in estradiol and free estradiol.
Another study done by Adam et al in 2016, compared men on a high fat diet of 60% and moderate fat diet of 30%. In the high fat group, there was an increase in testosterone levels by 15% on average, indicating benefits of a high fat diet.
Dorgan et al (1996) compared low fat to high fat diet as well. The study had a crossover design and included 43 healthy men aged 19-56. Men were initially randomly assigned to either a low-fat, high-fiber or high-fat, low-fiber diet for 10 weeks, and after a 2-week washout period, crossed over to the other diet. High fat diet contained 41% of fats while a low fat diet had 18% of fats. Testosterone levels were higher in high fat group by an average of 13%. Conversely, their urinary excretion of estradiol and estrone and their 2-hydroxy metabolites were 12-28% lower with the high-fat, low-fiber diet as well.
We can see that there is a clear advantage of a higher fat approach when it comes to increasing testosterone and estrogen levels, but how does this help up grow more muscles?
How testosterone affects your strength and muscle growth
Testosterone activates androgen receptor, which signals your muscle cells to start producing more protein to grow. The more testosterone you have, the greater the muscle growth. As testosterone decreases, so does the muscle growth. Now you might be wondering if natural increase in testosterone is significant enough for muscle growth compared to the testosterone from an injection? Studies have concluded that changes in testosterone, even within drug-free range, can result in significant muscular growth. Testosterone can be increased of up to 30% just by improving the diet. Androgen levels can also be a significant determinant of nutrient partitioning during a caloric surplus. The higher the testosterone, the more of a caloric surplus will go to creating lean mass tissue instead of fat.
It is clear that testosterone has positive effects for muscle growth in men, but what about women? Again, very similar effects where testosterone levels can determine 66 to 90% of how fast women gain strength and power. We will discuss about this in more detail later in the article.
How does testosterone affect muscle growth?
With testosterone increase, muscle growth does not come instantly. Instead, it takes months for changes to be noticeable. Even steriod users, with testosterone levels 10 times the normal amount cannot see the major difference within the first month. For naturally boosted testosterone, it takes even longer.
Testosterone increases muscle growth through myonuclear addition. Your muscles contain a nuclei that function as a command center in their region for muscle fibers. These nuclei contain a blueprint to create new proteins. What this means is, the more nuclei you have, the more muscle growth you can achieve. The trick is, there is a ceiling to number of nuclei you can have in a muscle, and that ceiling is mostly determined by your testosterone level.
The way nuclei number increases is through satellite cells that activate after you engage in a high intensity exercise to repair the damage. These cells fuse to muscle fibers and donate a new nuclei to the muscle, therefore, increasing the number of nuclei in the muscle.
This process of donation is aided by testosterone. The more testosterone you have, the greater the nuclei addition and more muscle growth you can achieve. The thing is, this is a slow process that takes time to accumulate and become noticeable.
On a side note, any additional nuclei that was donated to the muscle tissue is permanent, which explains muscle memory and why it is easy to build back any lost muscle.
Estrogen is not really a bad guy after all
Estrogen is widely regarded as catabolic and fattening hormone, but this reputation is completely undeserved. First of all, it has many beneficial effects for women like:
Aiding muscle repair
Is anti catabolic and prevents muscle damage and loss
It decentralizes your body fat distribution which improves metabolic health
It protects joints, bones and tendons from injury
Reducing fat intake can therefore seriously impair muscle growth and strength progression for women.
The second reason why women should eat more fat is because they burn less carbohydrates and more fat during exercise. Since women do not burn as much carbs, they also do not store as much carbs as glycogen during carb refeeds and estrogen is partially responsible for this.
Because women have a glycogen sparing metabolism, they should eat more fats instead of carbs. Numerous studies show cardiovascular and hormonal benefits of eating fats for women.
Low fat diet can also reduce breast size (obviously this does not apply if you have breast implants) as estradiol and IGF-1 levels are correlated with breast size. Another reason why high fat diets are good for women is because they are more satiating (around 15%) compared with men.
If all of this is not enough to convince you, there is more! Fats do not decrease as much insulin sensitivity in women compared to men because of estrogen. This keeps the inflammation in check. This also means that polyunsaturated fats are less likely to be oxidized which makes them available for anabolic effects.
This fatty acid directly increases muscle protein synthesis through several ways:
Omega 3 can lower chronic inflammation and increase acute inflammation as a result of resistance exercise. This can help with muscle repair and growth due to a better signal.
Omega 3 protects against excessive muscle damage.
Omega 3 can lower cortisol (stress hormone) levels.
Omega 3 can increase testosterone production
Omega 3 can increase muscle anabolic signaling and protein synthesis after meals.
Omega 3 increases thermic effect of a meal by 50%.
Omega 3 increases fat oxidation rates making you leaner.
Omega 3 increases your metabolism by increasing protein synthesis and lean body mass.
Recommended intake for omega 3 is 3 g of EPA and DHA combined either through supplementation or fatty fish like salmon.
Studies show that omega 6 also has anabolic benefits. Few studies showed up to 3 times more muscle growth compared to consuming only saturated fats. However, because omega 6 is pro inflammatory, a ratio of up to 1:4 of omega 3 to omega 6 should be the maximal limit. This means that you should also include other types of fats.
Similarly, reasearch shows that mono-unsaturated fats can also decrease chronic inflammation levels which can lead to better anabolic signaling and more muscle growth. A study done by Noakes et al (2006) comparing fat loss with 3 different types of diets. One of them was a high unsaturated fat diet, where participants had a significantly less lean body mass loss over the course of the diet.
Saturated fat (SF) does not have a direct anabolic effect like omega 3 and omega 6, but it does increase testosterone levels over time simply by increasing your fat intake. The main concern with saturated fats is, of course, health. It is believed that SF increases your cholesterol levels and clogs up your arteries, but is this really true?
This is a theory that originated all the way back from 1952 when Ancel Benjamin Keys developed a hypothesis saturated fats increase cholesterol levels, specifically worsen the cholesterol profile by increasing LDL cholesterol, which eventually clogs up your arteries. However, this hypothesis was never supported by direct controlled research in humans.
The vast majority of the research does not support that SF does increase cholesterol levels. Some research even finds positive effects of SF on blood cholesterol levels, increasing the level of HDL (good cholesterol) without any effects on LDL (bad cholesterol).
In 2015, a meta-analysis showed that replacing saturated fats with carbs or protein offered no health advantages.
What matters with saturated fats is food source, and staying away from heavily processed foods will minimize any potential risk. Overall, saturated fats have a neutral effect on your overall health, and should be incorporated in your overall diet.
How much fat should we consume exactly for optimal anabolic effect? It differs between men and women. For men, recommended fat intake starts at 20% of total caloric intake as a minimum, and goes up to 40% of BMR (basal metabolic rate) as a maximum. If going all the way up to 40% causes you to decrease carbohydrates to a very low level, lower the fat intake by 10-15%.
For women, the upper limit is 40% of REE (resting energy expenditure) as they have a glycogen sparing metabolism and can burn fat more efficiently. Other hormones like estrogen can also benefit from a higher fat diet.
The exact ratios of the type of fats are not as important as long as you consume 3 g of omega 3, and a mix of different unsaturated fats. The rest can be filled with some great saturated fat sources like dark chocolate, dairy, coconut and meat.
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