Fat is essential for proper hormone production.
That statement is fact. Fat helps regulate the production of hormones in the body, including testosterone. The necessary level of fat can be debated, but the American Heart Association recommends 20-35% of daily calories come from fat.
Thus, for a 2,000 calorie a day diet, that is 400-700 calories or 44-78 grams of fat per day. This is what the body will require to produce optimal levels of hormones and also to function properly.
Since fat is linked to adequate testosterone, one would think that a ketogenic diet or another higher fat diet would lead to even higher levels of testosterone and advocates for these diets have even promoted that. Or, at the very least, it wouldn't have any negative effect on hormone levels, right?
Your keto diet might be turning you into a woman! Well, maybe not that extreme, but it appears that it might be possible to have too much of a good thing. Can low carb, or ketogenic diets lower your testosterone?
Based on available data, it absolutely can!
Firstly, glucose is responsible and plays a huge role in GnRH levels which lead to hormonal actions in the body. GnHR is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary.
These are all critical to the production of testosterone and other hormones. This can be one reason why these studies I am about to mention turned out the way they did. 
When carbs were reduced to 30% of one's diet, even more carbs than most ketogenic diets recommend, testosterone and the ratio of testosterone to cortisol was reduced significantly in subjects. This wasn't just in normal people - this was also replicated in Olympic athletes. 
Cortisol levels skyrocketed as the athletes depleted glycogen and increased the cortisol to testosterone ratio in these highly-trained athletes. The effect was blunted and reversed with the inclusion of a carb-containing shake.
This is even more evidence than when I recommend a shake with MTS Nutrition Machine Whey and Machine Carb 10 IMMEDIATELY post workout, regardless of diet, you are doing great things for more than fat loss, but for recovery and hormone response to training. 
I recommend a balanced diet, as found in the Drop Factor Book, so don't think we are advocating super-high carbohydrate diets, but the evidence to include carbs in your diet is hard to ignore. In one study, high carb diets increased testosterone by 36% over low carb diets.  The carb group also had lower levels of the stress hormone, cortisol.
But I was told that carbs make you fat?
Contrary to what the people trying to sell you stuff or sell books or simply have befriended Oprah, diet is pretty simple and regardless of what your diet beliefs are, there is one thing we all agree upon:
Exercise is Awesome
Diet is very important, but to ward off a lot of lifestyle diseases like type-2 diabetes and obesity, a consistent exercise plan should be a part of your life. We have a TON of options available at TigerFitness, but the training found in the Drop Factor Book is a great option!
Back to Diet
The main variable to losing fat and gaining muscle is caloric balance. Take in more calories than you burn and you will gain weight. Take in less than you burn and you will lose weight. Some simple dietary rules of thumb:
- Set protein to 1-1.5 grams per pound of bodyweight daily.
- Set Fat to 0.3-0.5 grams per pound of bodyweight daily.
- Fill in the rest of your caloric needs with carbs.
- Find your TDEE, or Total Daily Energy Expenditure HERE (How many calories you need per day).
- Find the macronutrient breakdown you want and calculate macros based on your TDEE here.
- As stick point are hit if losing fat, drop carbs by ~40-60 grams per day (based on weekly progress to lose 1-2 lbs a week) or increase activity (cardio).
- As stick points are hit if trying to gain mass, increase carbs by ~40-60 grams per day (based on weekly progress to gain .5-1lb a week) or just check out Mass Diet.
The Take Home
I wouldn't worry about keto lowering your testosterone one bit. If you enjoy the diet, DO IT!
Sticking to it will be much better than a free-for-all of fat gain. But the message here is that there is no perfect diet. Do what works for you and please check out all of the resources in this article to help you find the perfect diet.
Please comment down below what work best for YOU so that your experiences can help out fellow readers!