Why sleep matters when it comes to diet

When people come to see me, they expect me to ask about what they eat and their level of physical activity. But they can be surprised when I ask them about their sleep patterns.

As a nutritionist, I am interested to all aspects of one’s lifestyle that might interfere with health and diet, and sleep is a big one.

And how Shakespeare said so well in Macbeth, sleep is the “Chief nourisher in life’s feast.”

“Sleep that knits up the ravell’d sleeve of care,

The death of each day’s life, sore labour’s bath,

Balm of hurt minds, great nature’s second course,

Chief nourisher in life’s feast. “

Macbeth (2.2.46-51), William Shakespeare

We know that many of our physiological functions are regulated by an internal biological clock. Body temperature, hormone levels, sleep, behaviours, metabolism, these follow a circadian rhythm.

In the morning our body temperature is low, and our blood pressure rises. Our glucose response is optimal, and our body knows exactly what to do with all the energy we ingest.

In the afternoon, we have our best coordination and muscle strength.

And as the day light withdraw, the melatonin hormone is secreted, signalling the need to wind down so that, at night, the cellular regeneration process can begin.

Our body can cope with us messing up with this central clock, from time to time. But if chronically disturbed and our sleep damaged, this hinder many of our metabolic and hormonal functions. And such changes are likely to impact aspects of our nutrition and body weight[1],[2].

And with 34% of UK population reporting short sleep duration (i.e., less than 7hours a night), this issue is particularly relevant as a wellbeing matter, beyond feeling simply a bit tired.

Here is some of the findings from recent research about sleep disruption:

Increased hunger and food cravings

Not only has lack of sleep has effect on our on appetite regulating hormones such as leptin (satiety), ghrelin (hunger)[3] leading us to feel hungrier and less satisfied, but it also changes our food preferences. When sleep deprived, we tend to seek more energy dense and palatable foods[4].

Increased body weight and fat mass

With heightened hunger signals and dampened feeling of satiety, it is not surprising that poor sleep is associated with higher body weight [5]. But that is not it. The weight in short sleepers seems to be more specifically located around the waist – just where it hurts the most.

This extra weight might also be explained by a change in our energy expenditure, as we are less likely to engage in as much physical exercise, in terms of volume and intensity, when sleep deprived.

Insulin resistance

In addition to appetite hormones, the lack of sleep seems to play up with our ability to regulate our blood glucose levels.

When we eat food high in glucose, we secrete insulin, a hormone that signals to our liver the need to keep our blood glucose levelled. But sometimes the liver is a bit slow at receiving the message – this is call insulin resistance which can eventually lead to developing type 2 diabetes. Poor sleep is linked to this mechanism of insulin resistance.[6]

Altered gut microbiota?

A fascinating field of research in nutrition is the gut microbiota: this colony of micro-organisms that populates our gut and modulates our immune functions, inflammation, mood, weight.

This microcosm is highly sensitive to our lifestyle: our diet, our physical activity, our stress. All of these may shape up the profile of our gut microbiota (in terms of size, type of bacteria, and overall balance) which will in turn affects positively or negatively our health.

So, it is not surprising that some researchers suspect sleep deprivation to have a negative effect the gut microbiota and its overall balance. But this is early in the world of research -to date, evidence is scarce and mostly on rodents[7], so we will to be a bit patient to link the two.

So what can you do to improve your sleep?

Duration of sleep matters – adults needs between 7 to 9 hours of sleep for optimal health. But sleep quality is important too. Have a look at the 7 steps to better night’s sleep from The Sleep Council https://sleepcouncil.org.uk/advice-support/sleep-advice/7-steps-to-a-better-nights-sleep/

And here are a few key points:

· Make your room completely dark and at a cool temperature of 16-18ºC

· Avoid screen in your bedroom and in the 30-60mins leading up to bed

· Keep the lighting dim in the evening

· Have regular sleeping patterns, weekdays and weekends.

· Mind alcohol and caffeine as these can hinder your sleep quality

· Avoid eating in the 2 hours before bedtime.

· Be physical active during the day but don’t over do it.

· Consider yoga or medication to help with relaxation

So, how is YOUR sleep? Could you make it work better for you?

Taking care of your sleep might help you make better food choices, exercise more and support your metabolic health.

And remember, wellbeing is a jigsaw from which diet, exercise and sleep are only some of the pieces. Pollution, culture, stress, occupation – all these, also will influence our overall health and how we eat. Some are in our control, some don’t but knowing the role they play can really help shape our efforts in the right direction.

References

[1] Geiker NRW, Astrup A, Hjorth MF, Sjödin A, Pijls L, Markus CR. Does stress influence sleep patterns, food intake, weight gain, abdominal obesity and weight loss interventions and vice versa? Obes Rev. 2018 Jan;19(1):81-97. doi: 10.1111/obr.12603. Epub 2017 Aug 28. PMID: 28849612. [2] Gangwisch JE. Epidemiological evidence for the links between sleep, circadian rhythms and metabolism. Obes Rev. 2009 Nov;10 Suppl 2(0 2):37-45. doi: 10.1111/j.1467-789X.2009.00663.x. PMID: 19849800; PMCID: PMC4075056. [3] Spiegel K, Tasali E, Penev P, Van Cauter E. Brief communication: sleep curtailment in healthy young menis associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. AnnIntern Med 2004; 141: 846–850. [4] St-Onge M-P, McReynolds A, Trivedi ZB, Roberts AL, Sy M, Hirsch J. Sleep restriction leads to increasedactivation of brain regions sensitive to food stimuli. Am J Clin Nutr 2012; 95: 818–824 [5] Cooper CB,Neufeld EV, Dolezal BA, et al. Sleep deprivation and obesity in adults: a brief narrative review. BMJ Open Sport & Exercise Medicine 2018;4:e000392. doi:10.1136/ bmjsem-2018-000392 [6] Esra Tasali, Rachel Leproult, Karine Spiegel, Reduced Sleep Duration or Quality: Relationships With Insulin Resistance and Type 2 Diabetes, Progress in Cardiovascular Diseases, Volume 51, Issue 5, 2009, Pages 381-391, ISSN 0033-0620, https://doi.org/10.1016/j.pcad.2008.10.002. [7] Poroyko, V., Carreras, A., Khalyfa, A. et al. Chronic Sleep Disruption Alters Gut Microbiota, Induces Systemic and Adipose Tissue Inflammation and Insulin Resistance in Mice. Sci Rep 6, 35405 (2016). https://doi.org/10.1038/srep35405