The Hormonal Effects of Cutting Carbs Too Much

When it comes to nutrition, carbs often get an undeserved bad rap. While cutting back on refined sugars can benefit blood sugar and energy levels, slashing carbohydrates too drastically can set off a ripple effect throughout your hormonal system. From cortisol and thyroid hormones to those that regulate appetite, reproduction, and mood low-carb diets can lead to changes that affect how you feel, function, and even sleep.

Let’s explore how your body responds hormonally when carb intake drops too low for your individual needs.

1. Cortisol May Rise to Compensate for Missing Glucose

Carbohydrates are more than just a fuel source they’re a signal of energy availability. When carbs are too restricted, the body may respond by increasing cortisol, the primary stress hormone, to help raise blood sugar by releasing stored glucose from the liver.

In the short term, this is part of a natural survival mechanism. But chronically elevated cortisol can lead to:

• Feeling wired but fatigued

• Midday energy crashes

• Heightened sugar cravings

• Increased stress levels even without external stressors

In fact, one study in The Journal of Nutrition found that low-carb diets led to significantly higher cortisol levels compared to higher-carb diets, even when calorie intake was the same.

2. Thyroid Function Can Slow

Your thyroid relies on adequate glucose to convert the hormone T4 into its active form, T3. Without enough carbs, this conversion can falter slowing metabolism, making you feel cold, and zapping your energy.

Research has shown that people on very low-carb diets may experience decreased T3 levels independent of how many calories they’re eating. Signs your thyroid may be affected include:

• Feeling cold more often

• Unexplained fatigue

• Slowed weight loss despite consistent effort

3. Insulin and Glucagon Patterns Shift

Cutting carbs affects the balance between insulin and glucagon two key hormones that regulate blood sugar. Insulin typically decreases with low-carb intake due to reduced glucose, while glucagon increases to help maintain blood sugar by tapping into energy reserves.

This shift can make your energy feel less steady, showing up as:

• Irritability or shakiness between meals

• Low energy during workouts

• Intense hunger when meals are delayed

According to the CDC, nearly 38% of adults in the U.S. have prediabetes, often tied to poor glucose regulation so these hormone patterns matter even more if you’re already navigating blood sugar challenges.

4. Appetite Hormones Adapt in Complex Ways

While you might assume that fewer carbs equals more hunger, long-term low-carb diets can actually lead to improved sensitivity to leptin, the hormone that signals fullness. In many cases, ghrelin (your hunger hormone) also stabilizes, and other satiety hormones like CCK increase.

You might notice:

• Feeling full more quickly during meals

• A reduced urge to snack

• More predictable hunger patterns

Still, these benefits can be highly individual and may take time for the body to adjust.

5. Reproductive Hormones May Be Suppressed

For people with ovaries, consistently low carbohydrate intake especially when combined with lower overall calories can signal to the body that energy is scarce. This can suppress reproductive hormone activity, disrupting menstrual cycles.

Leptin plays a role here too. When levels drop due to inadequate carb intake, the brain may reduce production of hormones like GnRH, which are essential for ovulation. Over time, this can lead to:

• Irregular or missing periods

• Heightened PMS symptoms

• Lower energy during the second half of your cycle

Functional hypothalamic amenorrhea, often triggered by low energy availability, is more common than many realize especially among active women or those following strict diets.

6. Serotonin Levels May Dip, Impacting Mood

Carbs help the brain produce serotonin by making it easier for tryptophan to cross the blood-brain barrier. When carbs are scarce, less serotonin is produced potentially influencing mood, sleep, and emotional regulation.

This may look like:

• Feeling irritable or low

• Increased cravings for comfort foods

• Trouble falling asleep or winding down

Low serotonin is also tied to increased anxiety and depressive symptoms, especially in women, who are statistically more sensitive to changes in serotonin than men.

If you found this article helpful, consider sharing it or subscribing to our newsletter for more like it.