Let’s talk about sleep and sugar! Sleep is more than just dreaming and resting your body. In fact, if we could bottle up the miraculous benefits of sleep into a pill, everyone would be lining up to take it. Did you know that even one night of poor sleep can affect how your body uses insulin? If you’re looking to improve blood sugar regulation, prioritizing sleep should be one of your top focuses. 

Sleep involves a complex physiological process that unfolds in various phases throughout the night. Each night, our bodies ideally go through 4–6 “sleep cycles,” with each cycle lasting approximately 90 to 120 minutes. These sleep cycles consist of four stages, generally categorized into non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. Both types of sleep are essential for overall health. NREM sleep focuses on physical repair, while REM sleep plays a crucial role in cognitive functions like memory and learning (3-8). 

The Four Stages of Sleep 

Below, we’ve outlined the four stages of sleep, their categorization as NREM or REM, and a brief look at what happens in each stage (13). 

Stage 1 NREM  

This is the hazy period when you first start to fall asleep. Your brain activity slows down slightly, and you’re not fully asleep yet. It’s easy to wake up during this stage, which typically lasts 1–5 minutes. During this time, you might not even be aware if you’re awake or asleep (9). 

Stage 2 NREM  

In this stage, your heart rate and breathing slow down, your internal body temperature drops, and your muscles relax. This is a deeper sleep phase, with eye movement stopping and brain waves showing new, slower patterns. Although brain activity decreases, there are still bursts of activity that help prevent you from waking up due to external stimuli. Stage 2 accounts for about 45% of total sleep time and typically lasts around 10–35 minutes per cycle (9). The duration of Stage 2 is shortest in the first sleep cycle and gradually lengthens as sleep progresses. 

Stage 3 NREM 

This is the deep sleep phase, characterized by large, slow brain waves known as delta waves. Often called slow-wave sleep, this stage involves reduced brain activity, allowing the body to repair tissues and promote growth. Muscles are at their most relaxed here, minimizing further strain and aiding recovery. Without enough Stage 3 sleep, maintaining consistent energy throughout the day can be challenging. It’s difficult to wake up during this stage, as your body focuses on tasks like muscle repair, converting short-term memories into long-term ones, and regulating hormone levels. Stage 3 begins around 40 minutes into the first sleep cycle and then shortens to about 20 minutes in subsequent cycles (13). 

Stage 4 REM 

This is the stage where dreaming occurs. You typically don’t enter REM sleep until about 90 minutes into your sleep. In this phase, your brain activity becomes as high as when you’re awake, while your body remains still except for rapid eye movements. REM sleep is crucial for memory enhancement, emotional processing, creative thinking, and problem-solving (14). Each REM cycle increases in length, starting at about 10 minutes and extending up to an hour by the end of the night, ultimately making up around 25% of an adult’s total sleep (13). 

The Importance of Uninterrupted Sleep for Metabolic Health 

Each sleep stage serves a specific and essential purpose. When it comes to insulin sensitivity and improved metabolic outcomes—like better blood sugar regulation and weight management—stages 3 and 4 are particularly crucial. This is why uninterrupted sleep throughout the night is so important. 

When sleep is interrupted, whether from waking up to use the bathroom, chronic pain, or untreated sleep apnea, the body returns to Stage 1 once sleep is resumed. This can happen with even a split-second wake-up (as in sleep apnea) or several minutes of being awake (such as letting the dog out). Even if you fall back asleep quickly, it may take approximately 10–35 minutes to re-enter Stage 3 if you wake up during Stage 2. Essentially, this could result in missing an entire cycle of stages 3 and 4, making it harder to lose weight and manage blood sugar effectively. 

Focusing solely on the number of hours slept may not be enough for achieving optimal metabolic health. Waking up in the middle of the night and disrupting your sleep cycle is just one factor that can impact sleep quality and, ultimately, your metabolic wellness. 

High-Quality Sleep 

High-quality sleep refers to how well you sleep, measured by factors like how long it takes to fall asleep, the number of times you wake up for more than 5 minutes, how long you stay awake after initially falling asleep, and the overall quality of your sleep (15). Signs of high-quality sleep include waking up feeling refreshed and alert, along with being able to stay awake and attentive throughout the day without experiencing significant fatigue. If you journal, you may notice improved moods on days after high-quality sleep. 

Wearable devices can help track your sleep patterns, heart rate, and movement during rest, providing insights into sleep quality. When red flags appear, such as excessive fatigue, low mood, or concerning measurements like heart-rate variability, nighttime movement, or reduced time in each sleep stage, it may be especially helpful to focus on Stages 3 and 4 for improvements. 

Improving Stages 3 and 4 of Sleep 

Let’s look at some ways to enhance deep sleep for better health: 

1. Maintain a Consistent Sleep Schedule: Go to bed and wake up at the same time every day, even on weekends. Consistency helps regulate your body’s internal clock and promotes deeper, more restful sleep. 
2. Create a Relaxing Bedtime Routine: Establish a calming bedtime routine to signal to your body that it’s time to wind down. This routine could include reading, talking with a partner, taking a warm bath, practicing relaxation techniques like deep breathing or meditation, or gentle stretching. 
3. Optimize Your Sleep Environment: Make your bedroom favorable to sleep by keeping it cool, dark, and quiet. Use blackout curtains or an eye mask to block out light and consider white noise or earplugs to mask disruptive sounds. A small study found that people sleeping with lights on had higher heart rates, spent more time in stage 2 sleep, less time in slow-wave and REM sleep, and experienced impaired glucose homeostasis. These findings are relevant for people frequently exposed to nighttime light, as they may face an increased risk of type 2 diabetes (17). 
4. Limit Stimulants and Electronics Before Bed: Avoid caffeine and alcohol in the hours leading up to bedtime, as they can interfere with deep sleep. Limit exposure to blue light from screens before bed, as this can disrupt sleep patterns. Consider using blue light-blocking glasses as well. 
5. Move Regularly: Engage in regular physical activity, but avoid vigorous exercise close to bedtime, as it can be stimulating. Aim to be active on most days, preferably earlier in the day. 
6. Manage Stress: Practice stress-reduction techniques like mindfulness meditation, stretching, or progressive muscle relaxation to calm your mind and body before bed. Progressive muscle relaxation involves tensing and then slowly relaxing each muscle group to reduce physical tension and stress. This can help decrease the anxiety that interferes with deep sleep, making stress management essential. 
7. Evaluate Sleep Aids: Certain antidepressants and medications may significantly reduce stage 4 sleep. If you take these medications, discuss their effects on sleep with your healthcare provider and explore possible alternatives. 
8. Consider Magnesium- and Melatonin-Rich Foods: Incorporate foods rich in magnesium and melatonin into your diet to naturally support sleep. Magnesium-rich foods include leafy greens (spinach, kale, Swiss chard), nuts and seeds (almonds, pumpkin seeds, sunflower seeds), and whole grains (brown rice, quinoa, oats). Magnesium glycinate is often recommended to enhance muscle relaxation and improve stages 3 and 4 of sleep (18). Some medications, like hydrochlorothiazide and omeprazole, may increase the risk of magnesium deficiency. Always consult your healthcare provider before starting or stopping any supplement or medication. Melatonin-rich foods include tart cherries, almonds, walnuts, and grapes. 

Finding the Right Balance: How Much Sleep is Enough? 

When it comes to sleep, there’s no universal answer to the question, “How many hours are ideal for optimal metabolic health?” Factors like age, genetics, activity level, previous sleep deprivation, and sleep quality all influence individual sleep needs. For instance, better-quality sleep can reduce the overall hours required to feel rested. Research, however, indicates that getting less than 6 hours of sleep per night is linked to higher fasting blood sugars, elevated triglycerides, and increased waist circumference (11-13). Conversely, more sleep isn’t always better—consistently sleeping over 10 hours can raise fasting blood sugar levels in women, and excessive sleep in both men and women has been associated with type 2 diabetes, cardiovascular disease, and obesity (11-13). 

Sleep is a vital process with a profound impact on health. Each stage, from the light sleep of Stage 1 to the deep, restorative sleep of Stage 3 and REM sleep, contributes uniquely to physical and mental well-being. High-quality, uninterrupted sleep is essential for optimal metabolic health, cognitive function, and emotional stability. Remember, it’s not just about how long you sleep but how well you sleep that truly matters.

Sending Health Your Way!

The Tula Clinical Team

Austin MS, RDN, CSR, LDN, CD
Aubree RN, BSN