Leaning out feels amazing. You look better, your self-confidence soars, and you're finally able to show off all that muscle you worked so hard to build.

But your body might not be quite so happy. Your body stores fat as a necessary safeguard against starvation, so it doesn't like to be exceptionally lean. A certain level of body fat is required to sustain proper function, which is why drastic diets can quickly throw your body into panic mode. 

So why does your body go haywire when you diet? Reducing your body fat with intense diets has a huge impact on your hormones, which regulate your mood, energy, and health. 

If you are planning to lean out, learn what you can do to maintain optimal hormone levels so you feel and function at your best. 

Leptin 

Leptin is produced by your fat cells and responds to three things: 

• Calorie intake 
• Carbohydrate intake
• Current body-fat levels

When your body fat decreases, your leptin levels decrease as well. Carbohydrate and calorie intake also have a huge impact on circulating leptin levels, so any significant changes to your diet will affect this hormone. 

So what happens when leptin drops? Leptin is designed to signal when energy intake is not being adequately met, at which time changes in the body will occur to try and balance things out. 

Some of the main things you'll begin to notice include:

• Insatiable hunger 
• Low libido 
• Decreased energy 
• Lowered strength and endurance 
• Feeling cold all the time
• Feelings of depression or decreased interest in normal activities 
• Decreased fat loss 
• Suppressed metabolic function 
• Slow healing, recovery, or both 

Sounds awful, right? That's why taking care of your leptin levels is so important. While it's impossible to completely avoid the metabolic slowdown that accompanies decreased calorie intake, you can prevent this shift from taking place too quickly. 

Slow Down, and Keep the Carbs

Clearly you must be in a calorie deficit to lose fat, but you can start with a moderate deficit rather than an aggressive one. Give yourself plenty of time to lean down so you don't have to cut calories by more than 500 per day. This will go a long way toward keeping your hormones happy. 

Also, keep your carbohydrate intake up as high as possible, for as long as possible. This is critical, as carbohydrate intake tends to impact leptin concentration more than protein or fat, as shown in research published in the Diabetologia journal.[1] When carbs dip down too low, the most aggressive shift in leptin occurs. By maintaining adequate carb intake while getting lean, you can help sidestep this side effect and maintain a more balanced state. 

If you absolutely must incorporate low-carb days, consider carb cycling as a more hormone-friendly approach. 

Finally, try implementing "refeeds" into your diet plan every so often. A refeed is a period of temporary overeating, usually lasting 1-2 days, where you significantly increase your carbohydrate intake. This shows the body there is an abundant supply of incoming calories, eliminating the need to downregulate metabolism and leptin.

Many of the unwanted symptoms of dieting—such as those noted above—greatly subside as the result of a refeed. The leaner you get, the more important these periods of high carbohydrate intake become for maintaining your metabolic health. 

Testosterone 

While women should also pay attention to testosterone, men tend to experience a more significant decline as they diet, which can diminish overall feelings of wellness, and hinder results. 

Testosterone is one of the most anabolic hormones in the body. When it starts to decline, loss of strength and muscle mass is likely to follow. 

Other symptoms of low testosterone may include: 

• Increased body fat 
• Poor sexual performance, decreased libido, or both 
• Feelings of depression 
• Low energy levels 

When you diet, the drop in total calorie intake and the decrease in total fat consumption interferes with testosterone production. Dietary fat is particularly important because cholesterol is a precursor for all sex hormones, including testosterone. If you want to keep your gains, don't cut all the cholesterol out of your diet! Some saturated fat in the diet can be a good thing.

In fact, studies confirm men who consume higher-fat diets with a lower volume of fiber tend to have greater overall testosterone levels compared to men on lower-fat diets with a higher volume of fiber.[2]

Cut Back on Cardio and Get More Sleep 

While some cardio may be warranted when trying to get lean, hours upon hours of cardio each week could negatively suppress testosterone production. Research confirms that men who introduce a high level of running into their program over a period of months typically see a decline in production of this powerful hormone.[3] 

Also, if you are trying to shed a few pounds of body fat, make sure you get enough sleep at night. While sleep in general is important for optimizing your testosterone levels, it will be even more vital while you are on a reduced calorie intake.

Research indicates that just one week of sleep deprivation lowers testosterone levels by as much as 10-15 percent.[4] So do yourself a favor and get at least 6-8 hours of sleep every night to avoid the dreaded testosterone dip.

Thyroid Hormones 

Thyroid hormones play a key role in regulating your resting metabolic rate and overall well-being. While clinical hypothyroidism should be treated by a proper medical professional, it is normal to see some thyroid downregulation when on a reduced-calorie diet plan, especially if it's for an extended period of time.

The best ways to optimize thyroid output include:

• Do not overtrain on a calorie deficit. Too much exercise will tax your body and may even cause your thyroid and central nervous system to become sluggish. Take it easy and don't be afraid to take a day off. 
• Manage everyday stress. You already have a high degree of stress being placed on your body from diet and exercise alone. The last thing your body needs is high stress in other areas of your life. Find ways to relax and unwind to manage your daily stress.
• Maximize your sleep. Allow your body adequate rest and sleep for full recovery of hormonal status while dieting. Think of sleep as the reset button for your hormones. 
• Maintain a moderate calorie deficit and sufficient carbohydrate intake. Research shows those put on very-low-calorie diets tend to experience suppressed resting metabolic rate and T3 values (a measure of thyroid output) even after refeeding has taken place.[5] This means your thyroid may not bounce back so quickly after drastic dieting, and you could do long-term damage to your hormone levels if you're not careful. So watch your intake.  

It's a good idea to get your thyroid tested prior to starting any major diet plan to ensure that your levels are optimal before you begin. A simple blood test can rule out hypothyroidism, which may require medical treatment to bring your output to a healthy level.

A Final Word

Whether you're just looking to get leaner for the upcoming beach season or are training for a competition, one thing is certain: People who don't take care of their hormones typically fail to see significant results because they feel miserable and drop off somewhere along the way.

Knowing more about how dieting affects hormones can help you take the necessary precautions to ensure success when you get lean. Changes to your hormone levels will naturally occur as you diet, but if you are smart in your approach, you can minimize the negative effects and reach your goals. 

References

1. Jenkins, A. B., Markovic, T. P., Fleury, A., & Campbell, L. V. (1997). Carbohydrate intake and short-term regulation of leptin in humans. Diabetologia, 40(3), 348-351.
2. Dorgan, J. F., Judd, J. T., Longcope, C., Brown, C., Schatzkin, A., Clevidence, B. A., ... & Taylor, P. R. (1996). Effects of dietary fat and fiber on plasma and urine androgens and estrogens in men: a controlled feeding study. The American Journal of Clinical Nutrition, 64(6), 850-855. 
3. Wheeler, G. D., Singh, M., Pierce, W. D., Epling, W. F., & Cumming, D. C. (1991). Endurance training decreases serum testosterone levels in men without change in luteinizing hormone pulsatile release. The Journal of Clinical Endocrinology & Metabolism, 72(2), 422-425. 
4. Leproult, R., & Van Cauter, E. (2011). Effect of 1 week of sleep restriction on testosterone levels in young healthy men. Jama, 305(21), 2173-2174.
5. Barrows, K., & Snook, J. T. (1987). Effect of a high-protein, very-low-calorie diet on resting metabolism, thyroid hormones, and energy expenditure of obese middle-aged women. The American Journal of Clinical Nutrition, 45(2), 391-398.