One of the most frustrating challenges on your fat loss journey isn’t always knowing what to do. You know what to do— you’re doing it, but still not making the progress you had hoped for. The frustrating part is understanding why.
If you’re reading this and thinking to yourself: Wait, I’m still stuck on the what-to-do (or where to start) part for fat loss— don’t worry, keep reading. This will only help shed more light on the important factors that either contribute to or hinder fat loss. While there may be several different areas that are inhibiting your progress, I want to discuss an area that is often overlooked: Sleep.
Specifically how sleep, or lack thereof, plays a critical role in body composition.
Most of us are aware that improved sleep quality will enhance our energy throughout the day, however with busy schedules, obligations, and responsibilities of daily life, improving sleep is a luxury a lot of us can’t afford. The purpose of this article isn’t to tell you how to better organize your time to sleep more. Rather, it is to help you truly understand reasons why improving your sleep will benefit you along your journey and explore how it directly influences all of the many components contributing to body composition.
There are numerous studies that look closely at the relationship between sleep quality and: body composition, weight loss outcomes, dietary intake, and quality of life.
It’s well documented that improved sleep quality increases physical activity and improves dietary intake. Conversely, poor sleep quality reduces physical activity as well as nutrient intake. This study observed the association between sleep metrics and body composition among 212 men and 218 women, both middle-aged, who were active anywhere between 1.5-6 hours daily (no, this doesn’t necessarily mean lifting weights or doing cardio for this long). The findings indicated that those who: went to sleep before midnight, woke up before 8AM, slept greater than 7 hours, and fell asleep within 12 minutes of lying down all had less body fat percentage and a lower BMI. Conversely, those who fell on the opposite sides of the data all had a higher body fat percentage and a higher BMI. Concluding overall, that improving sleep quality parameters is proven to be an effective tool for improving weight loss programs.
What can you take from this?
Improved sleep quality increases physical activity
Improved sleep quality improves dietary intake (more on this later)
Improved sleep quality is highly correlated to improved biometric markers such as body composition and BMI
The authors did note that more research was needed to understand the complex association between sleep and health measures such as body composition when considering populations who are more physically active and manage their diets.
You might be thinking: Well, as long as I’m still in a caloric deficit, I should still continue to lose fat even if I fall outside of the parameters of the group who had better stats in the study. This is exactly what ran through my head as well, especially as a competitor, because I wasn’t always able to hit that 7+ hour mark of sleep each night. But of course, I was surprised again when I found another study reviewing the Influence of Sleep Restriction on Weight Loss Outcomes Associated with Caloric Restriction.
This is an incredible study that takes into account groups already in a caloric deficit. Thirty-six participants were divided randomly into an 8-week caloric restriction only group, or a caloric restriction and sleep restricted group. The sleep restricted group were deprived of sleep for approximately 1 hour, five nights out of the week in addition to being in a calorie deficit. Results of the study showed very interesting results, in that both groups showed a similar amount of weight, lean mass, and fat mass lost.
However— the calorie restricted group, without disturbances in sleep, had a significantly greater proportion of total mass lost as fat in comparison to the sleep restricted group.
What does this mean?
Despite both groups losing a similar amount of total weight, the group that was also sleep restricted had significantly LESS fat lost
The sleep restricted group had a greater amount of lean mass lost
Other metabolic functions were also measured, including ghrelin and leptin levels, as well as resting metabolic rate, and respiratory quotient RQ. Of these, the measures that stood out the most were the findings on Respiratory Quotient. Respiratory quotient is an indicator of metabolic fuel use in tissues typically ranging from 0.7 to 1.0, where a value of 1.0 is consistent with pure carbohydrate oxidation and a value of 0.7 is consistent with pure fat oxidation.
The good stuff?
The group that was only in a caloric restriction had a decrease in respiratory quotient, which suggests a transition toward greater fat oxidation at rest. Meaning, that if you are in a calorie deficit and do not have poor sleep quality, your body will shift toward greater fat burning mechanisms while at rest!
Improved sleep quality while in a calorie deficit is absolutely more beneficial and produces far greater body composition outcomes than being in a deficit and sleeping poorly.
So far we’ve covered improved sleep quality vs poor sleep quality, and up to this point according to the data, poor sleep quality has consisted of less than 7 hours of sleep. However, is there such a thing as too much sleep? Is it still considered poor sleep quality if average sleep times are greater than 9 hours?
In short, yes. There are negative health associations with very short, short, and very long sleep times such as: weight gain and obesity, performance deficits, diabetes, and poor mental and physical health. Additionally, not only does sleep duration influence positive or negative health outcomes, but the time at which we choose to sleep does too. A 2013 study, Dietary Nutrients Associated with Short and Long Sleep Duration, investigated the relationship between sleep duration, sleep times, and food variety as well as associations with nutrient categories in proteins, carbs, and fats.
It was noted that in several European countries, adolescents who slept for less than eight hours lived a more sedentary lifestyle and demonstrated unhealthy eating habits. In Japan, it was found that those with shorter sleep durations were also associated with unhealthy eating patterns such as a preference for foods higher in fat, missing breakfast, snacking, and eating outside of home-cooked meals. Interestingly, those who slept later into the day not only had less hours of sleep than those who slept at traditional times, but consumed significantly more calories after 8PM along with fewer servings of veggies. Perhaps the least shocking was the finding that later bed and rise times were also associated with an increased consumption of fast-food and caffeinated drinks and reduced consumption of dairy products.
As far as the differences in diet among the very short (<5 hours), short (5-6 hours), normal (7-8 hours), and very long (9+ hours) sleep groups— the lowest energy intake was found in both the short and long sleep groups. The greatest food variety was found in the normal (7-8h) group, with the least food variety found in both the very short (<5 h) and very long (9+ h) sleepers.
To further illustrate the point, This study indicated that those with insufficient hours of sleep were associated with irregular meal times and eating, excessive snacking habits and seasoning of food, and an inadequate amount of vegetables; ultimately engaging in habits that are more likely to cause lifestyle related diseases.
Key points:
7-8 hours is the most ideal amount of sleep for both performance as well as eating habits
Sleeping at traditional times (not too late to bed, not too late to rise) also increases likelihood of healthier food choices
Healthier eating habits support quality sleep
There are literally hundreds of studies investigating health outcomes in relation to sleep duration and sleep quality, with all signs pointing to better quality sleep:
Increases energy— which would increase productivity / activity
Improves food quality choices, timing, and appropriate caloric intake
Lowers likelihood of developing lifestyle related diseases
Increases quality of life
Another benefit that’s also prevalent is that the relationship doesn’t only work in one direction. We don’t need to improve sleep first in order to have a positive influence on food choices, or increase productivity— the opposite is also true. Improving activity in addition to healthier food choices also increases and supports quality sleep, which overall improves our quality of life. The takeaway is just that it can work that way, and sometimes this may be an easier place to start for some people.
You snooze, you lose.
References:
Capers PL, Fobian AD, Kaiser KA, Borah R, Allison DB. A systematic review and meta-analysis of randomized controlled trials of the impact of sleep duration on adiposity and components of energy balance. Obes Rev. 2015;16(9):771–782. doi:10.1111/obr.12296
Grandner, M. A., Jackson, N., Gerstner, J. R., & Knutson, K. L. (2013). Dietary nutrients associated with short and long sleep duration. Data from a nationally representative sample. Appetite, 64, 71–80. https://doi.org/10.1016/j.appet.2013.01.004
Imaki M, Hatanaka Y, Ogawa Y, Yoshida Y, Tanada S. An epidemiological study on relationship between the hours of sleep and life style factors in Japanese factory workers. J Physiol Anthropol Appl Human Sci. 2002;21(2):115–120. doi:10.2114/jpa.21.115
Poggiogalle, E., Lubrano, C., Gnessi, L. et al. Reduced sleep duration affects body composition, dietary intake and quality of life in obese subjects. Eat Weight Disord 21, 501–505 (2016). https://doi.org/10.1007/s40519-016-0254-z
Youngstedt, S. D., & Kline, C. E. (2006). Epidemiology of exercise and sleep. Sleep and biological rhythms, 4(3), 215–221. https://doi.org/10.1111/j.1479-8425.2006.00235.x
Xuewen Wang, Joshua R Sparks, Kimberly P Bowyer, Shawn D Youngstedt, Influence of sleep restriction on weight loss outcomes associated with caloric restriction, Sleep, Volume 41, Issue 5, May 2018, zsy027, https://doi.org/10.1093/sleep/zsy027