“Happy New Year! Auld Lang Syne! Hope your 2019 is amazing! What diet plan are you doing?! I am going to get abs this year! I have signed up for a shake diet! I am going to work out every morning, lunch and evening until my summer holiday! So excited to get started!”
… Sound familiar? With the clinking of champagne flutes and popping of party streamers ringing in the new year, so comes the talk of new diets, exercise plans and big changes from almost every human you interact with. Whether it is conversations on your first day back at work or cyber proclamations of change with immediate effect, the ‘new year new me’ chat is unavoidable. The majority of January health kicks often revolve around losing inches off your waistline and getting shredded while forgetting how these changes may alter one of the things vital for a healthy life; your brain. Let’s learn how healthy our new routines really are by exploring the effects cutting calories and muscle building has on our noggins.
Brain-y Pump: The relationship between exercise and brain function
We are all aware of the health benefits of exercise; from reducing obesity and lowering your risk of heart disease to genuinely just making you physically fitter and stronger. Many who maintain long-term exercise routines also experience cognitive improvements such as increased focus and attention and improved memory. It may be obvious, but while you are working out those biceps and triceps, you brain is also going through a workout too, juggling different chemicals and signals before, during and after you train. So whether you love cardio (you super humans), practice high intensity interval training (HIIT) or lift (bro), your brain will be reaping some huge rewards.
Cognitive Function: Attention and Memory
There is nothing like an exercise session to clear the mind and scientifically, it has been reported exercise in young adults improves their ability to learn. This can be seen straight after a session, demonstrated by a study showing an increased ability to learn vocab following running (1), or after prolonged periods of time, witnessed in adults with an average age of 33 undertaking a 3 month aerobic routine (2). The first of these studies showed that changes in cognition correlated to increased cerebral spinal fluid levels of brain derived neurotrophic factor (BDNF); a protein which promotes neuron survival; and catecholamines such as dopamine; a neurotransmitter which stimulates working memory and arousal (1). The effect of the long-term exercise routine performed in the second study revealed a potential increase in the production of new neurons (2). This was shown by a MRI-monitored increase in blood flow to the dentate gyrus; a sub-region connected to the memory-forming hippocampus and one of two brain regions where neurogenesis occurs. Overall, it appears short-term protein and neurotransmitter changes experienced following a workout can improve attention and short-term working memory, and if routines are sustained, these changes can facilitate the production of new neurons and enhance long-term memory (motivation for me to get to the gym tomorrow).
Preventing Brain Degeneration
As we age, many individuals experience problems with memory and learning, which can sometimes be correlated with a decrease in hippocampal volume. However, some studies have reported that increasing physical activity in elderly people promotes their ability to learn and maintain memory. Correlation between cognitive ability and walking level was noted in a study involving around 5000 elderly women over a 6 year period (3). This relationship has since received a bit more of a scientific unpinning by an imaging study revealing the loss of frontal and temporal grey matter, which accompany ageing, is reduced in those who undertake cardio exercise (4). A relationship between exercise and improved cognition in those who carry Alzheimer’s disease risk gene alleles (APOE-e4) has been noted (5). However, much more work needs to go into the fundamental mechanisms underlying all these relationships between exercise and the elderly to see how much therapeutic weight they may hold.
Mechanisms
From the studies mentioned, there does appear to be a relationship between exercise and improved cognition. The potential neuro-mechanisms underlying these changes are still under investigation in animal models (more can be read in reviews (6,7)) but some changes thought to occur are:
Neurogenesis: the production of new neurons in the dentate gyrus
Increased LTP: increased strength between synaptic connections in the hippocampus and up-regulation of genes involved in this process
Increased angiogenesis: formation of new blood vessels in the brain
New dendritic spines (post-synaptic terminals): new connections can be made with existing neurons in hippocampus. New neurons produce mature spines quicker.
Reduced inflammation: increased levels of growth factors and their signalling
A lot of work is still required to pin down how us going to circuits makes us better learners but the is almost certainly a relationship there, so book your next class now!
Calories are King: Dietary Restriction and The Brain
Along with the new workout routine normally comes a ‘healthy eating’ plan too. The majority of these plans work on the basic science of caloric restriction. Your body naturally burns calories (technically defined as the energy needed to raise the temperature of 1 gram of water through 1°C) every day and we eat food to give our body the energy it needs to function. Weight is gained when more calories are consumed than needed, leading them to be stored as fat. All humans need body fat but nowadays, people can easily eat to excess, with one takeaway of a medium ‘veggie volcano’ pizza from Dominos plus a coke and a mars bar racking up a total of about 2000 kcal. Everyone burns different levels of calories per day (see how much you burn here), so the key is to eat slightly under this number added to the calories you burn from exercise to lose weight. So, bin off those shake diets and eat a healthy balanced diet on your specific number of calories. Simples and sustainable.
What does lowering calories do to the brain? The brain, like any other part of your body, requires energy from calories to fuel its actions. Despite its proportionally small size, the brain uses around 20% of the total calories needed to keep your body functioning. A highly debated argument is that small reductions to your required calorie intake, without compromising on nutrients, can have benefits to your cognitive function. This is related to dietary restriction (DR) and improved longevity (8), thought to be caused by reduced cellular inflammation and increased autophagy. An example of such study showed elderly people under DR for 3 months had improved cognition compared to non-DR controls (9). Mechanistically, this could be caused by increased LTP as DR studies have shown that eating fewer calories can enhance synaptic plasticity in tandem with increasing anti-inflammatory mechanisms (10). These improvements are proposed to be mediated by reducing the levels of toxic free radicals in the brain and products from the gut microbiome, however the trigger for these mechanisms remains elusive. The research on DR is responsible for intermittent fasting diets you read about online when you eat about 2 pieces of bread and a grape for 1 day a week. Some rave about these diets, others hate them. It is all a matter of taste (...terrible pun).
Some consequences of DR have also been observed. Recently, a study on long term caloric restriction in monkeys described a 50% increase in lifespan but a huge loss of grey matter (neuron cell bodies) in the brain (11). The monkeys tested didn’t show symptoms of reduced cognition, but grey matter loss is not really something you want to mess with. Also, if calories are cut by over 60%, it can be detrimental to human survival (12). Cognitively, extreme calorie cutting can cause a condition called ‘brain fog’; symptomatically described by tiredness, anxiety and irritability. This condition was characterised under control conditions during world war II, when 36 soldiers volunteered to undergo 6 months of eating half the number of calories they needed while walking 22 miles a week to test if men could recover from long-term lack of nutrients (13). The results of this study found some of the soldiers suffered psychological damage; experiencing lethargy and anxiety while also developing obsessions with food. Upon re-feeding, most of the men stated it took them over a year to fully recover. Brain fog is thought to be caused by a lack of specific nutrients and vitamins (14), such as Vitamin B12, rather than low calories. However, removing high levels of calories from your diet makes it very hard to get the right levels of brain food. Therefore, extreme long-term calorie cutting should be avoided.
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To round up, your new years health and fitness resolutions have a huge impact on your brain. Keeping up exercise routines long term can potentially help your memory and attention, while monitoring what you eat may also have some benefits. However, extreme of either of these activities will lead to excessive calorie loss, which can be super unhealthy. So strike a balance; your brain needs a cheeky piece of cake every once in a while.
References: In case you want more deets
1. Winter B, Breitenstein C, Mooren FC, et al. High impact running improves learning. Neurobiol Learn Mem. 2007;87(4):597-609. doi:10.1016/j.nlm.2006.11.003
2. Pereira AC, Huddleston DE, Brickman AM, et al. An in vivo correlate of exercise-induced neurogenesis ( a traiter). 2007. doi:10.1073/pnas.0611721104
3. Yaffe K, Barnes DE, Nevitt M, Lui L-Y, Covinsky K. A prospective study of physical activity and cognitive decline in elederly women. Am Med Assoc. 2001;161:1703-1708.
4. Colcombe SJ, Erickson KI, Raz N, et al. Aerobic Fitness Reduces Brain Tissue Loss in Aging Humans. Journals Gerontol Ser A Biol Sci Med Sci. 2003;58(2):M176-M180. doi:10.1093/gerona/58.2.M176
5. Etnier JL, Caselli RJ, Reiman EM, et al. Cognitive performance in older women relative to ApoE-ε4 genotype and aerobic fitness. Med Sci Sports Exerc. 2007;39(1):199-207. doi:10.1249/01.mss.0000239399.85955.5e
6. Hillman CH, Erickson KI, Kramer AF. Be smart, exercise your heart: exercise effects on brain and cognition.(SCIENCE AND SOCIETY)(Report). Nat Rev Neurosci. 2008;9(1):58. doi:10.1038/nrn2298
7. van Praag H. Exercise and the brain: something to chew on. Trends Neurosci. 2009;32(5):283-290. doi:10.1016/j.tins.2008.12.007
8. Lee C, Longo V. Dietary restriction with and without caloric restriction for healthy aging. F1000Research. 2016;5(0):1-7. doi:10.12688/f1000research.7136.1
9. Witte A V, Fobker M, Gellner R, Knecht S, Floel A. Caloric restriction improves memory in elderly humans. PNAS. 2009;106(14):1255-1260.
10. Hadem IKH, Majaw T, Kharbuli B, Sharma R. Beneficial effects of dietary restriction in aging brain. J Chem Neuroanat. 2017;95(October 2017):123-133. doi:10.1016/j.jchemneu.2017.10.001
11. Pifferi F, Terrien J, Marchal J, et al. Caloric restriction increases lifespan but affects brain integrity in grey mouse lemur primates. Commun Biol. 2018;1(1):30. doi:10.1038/s42003-018-0024-8
12. Speakman JR, Mitchell SE. Caloric restriction. Mol Aspects Med. 2011;32(3):159-221. doi:10.1016/j.mam.2011.07.001
13. Kalm LM, Semba RD. They Starved So That Others Be Better Fed: Remembering Ancel Keys and the Minnesota Experiment. J Nutr. 2005;135(6):1347-1352. doi:10.1093/jn/135.6.1347
14. Layer AM, Gómez-pinilla F. Brain foods: the effects of nutrients on brain function. Nature. 2008;9:568-576. doi:10.1038/nrn2421
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