Chapter 29
Cold Water and Hormesis to Eat to Your Heart’s Content
Our research has shown that positive benefits on mood and well-being are more evident with the more visual exposure to the sea. In other words, being able ‘to see the sea’ matters. This applies to all ages and some studies show that it is particularly evident as we get older. The sea is constantly changing and it is well known that variety enhances well-being. The sea is never the same on two consecutive days or even for a couple of hours within the same day. Thus a sea view is never boring, always stimulating. Proximity to the sea also increases the likelihood of engaging in physical activity, such as swimming (even cold water swimming!) and walking. Seaside living may also increase social interaction and provides a space for health and well-being – all well proven to increase lifespan. Whatever the reasons – and they are likely to be multiple – the benefits from being near the sea are strong and equivalent to the impact that factors like wealth have on health and added life years.
Whether we adopt cold water showers, cold water swimming or just spend time watching the sea, it is well established that this will benefit our health and well-being.
Chapter 9: Eat to Your Heart’s Content
THE FORBIDDEN MEAL, EATEN IN SECRET IN THE MIDDLE of the night, is one of my most cherished boarding school memories – the midnight feast. Usually, on a Saturday night, one of us was delegated to stay awake, check the coast was clear and rouse the other students at midnight, when we’d all sneak down to a large space under the staircase and proceed to share treats. These generally consisted of peanut butter and jam sandwiches and chocolate biscuits washed down with lemonade – nothing especially haute cuisine but mana from heaven for excited hungry schoolgirls. We were never discovered – the cat’s out of the bag now of course – and I have happy recollections of the pleasures of nocturnal feasting.
However, given the intervening accumulated wisdom, I’m now going to put a bit of a dampener on midnight feasts or even any between-meal snacking, which is a recipe for poor health for most of us. The human body, through thousands of years of evolution, is hard-wired to consume as much food as possible for as long as it’s available. In our early history, people hunted or gathered food and had brief periods of plenty, such as after a kill, and then potentially lengthy periods of famine. As humans were prey to large animals, they actively sought food during the day and sheltered and rested at night – so no midnight feasts.
Chapter 9: Eat to Your Heart’s Content
Prior to the advent of our electricity-powered society, people started the day at dawn, worked all day, usually doing manual labour, and then went to sleep with the setting of the sun. Human activity was synchronised to day and night. This allowed for natural control of over-consumption. Today, we are working, playing, staying connected and eating day and night. This adversely affects body clocks, which evolved to operate on a sleep–wake cycle, conditioned to daytime activity, moderate eating and night-time rest. Yet we find snacking on sweets and sugars appealing because it’s part of how we have evolved.
High calorie foods trigger dopamine release in ‘pleasure centres’ in the brain. These pleasure centres are linked by pathways that regulate biological clocks and physiological rhythms. Disruption of the pathways by eating high calorie foods, such as peanut butter and jam sandwiches between meals or during normal resting hours, results in the excess calories being stored as fat much more readily than if the same number of calories were consumed during normal feeding periods. The result is obesity and obesity-related diseases, such as diabetes and heart disease. As we get older, our sleeping patterns are disturbed and this may increase the likelihood of some of us heading to the kitchen at night to compensate with a quick snack. However, this will accelerate weight gain and it will not help with sleep. Bottom line: keep food intake to within an eight-hour window during the day if possible.
Chapter 9: Eat to Your Heart’s Content
What has this to do with ageing? Food consumption, diet, genes and pathways related to metabolism and cell energy production are the most important controllers for how our cells age. We eat so that we can have energy. Food produces energy. The rate at which energy is used up by the body is referred to as the metabolic rate, which is a series of chemical processes in each cell that turn the calories we eat into fuel to keep us alive. There are three main ways our body burns energy each day. The basal metabolism refers to the energy used for our body’s basic functioning while at rest. Next is the energy used to break down food and finally the energy used in physical activity.
An underappreciated fact about the body is that our resting metabolism accounts for a huge amount of the total calories we burn each day. Physical activity, on the other hand, accounts for a smaller part of our total energy expenditure – between 10 to 30 per cent (unless you’re a professional athlete or have a highly physically demanding job). Digesting food accounts for about 10 per cent.
Chapter 9: Eat to Your Heart’s Content
Two people with the same size and body composition can have different metabolic rates. We all have friends who fit into these categories – one can consume a huge meal and gain no weight while the other has to carefully count calories to avoid gaining weight. Whereas we don’t fully understand the mechanism that controls a person’s metabolism, we do know that the amount of lean muscle and fat tissue in the body, our age and our genetics change metabolism. We can change lean muscle mass and fat tissue but the other factors are of course fixed. Metabolism slows down as we age. This age effect starts early – at age 18 – and continues throughout life, so that at age 60 we burn significantly fewer calories at rest than at age 20. Consequently, we are more likely to put on weight and to develop an important new syndrome referred to as the metabolic syndrome, which is a set of conditions including increased blood pressure, high blood sugar, a large waistline and abnormal cholesterol or triglyceride levels. With metabolic syndrome, we are at an increased risk of chronic health issues, including heart disease, stroke and diabetes. Again, how this works, why these conditions cluster together into the syndrome in some people (estimated to be 30 per cent of people over 60 in our and other studies) and why it affects some people more than others remains unclear. Why our energy needs go down as we age even if we keep everything else pretty much the same is also a mystery. Basal metabolic rate – the number of calories required to keep the body functioning at rest – is calculated by putting height, weight, age and gender into an algorithm online which uses equations summarised from statistical data. While there are certain foods, like coffee, chili and other spices, that may speed up the basal metabolic rate up just a little, the change is negligible and short-lived and would never have an impact on waistline. Building more muscles, however, can be marginally more helpful. The more muscle on your body and the less fat, the higher your metabolic rate. If your metabolic age – calculated by comparing your basal metabolic rate to the average of your chronological age group – is higher than your actual age, it’s a sign that you need to improve your metabolic rate. Basal metabolic rate is closely linked to the size of an animal and to heart rate and is widely accredited for determining how long animals and possibly humans live for. In general, the smaller the animal, the faster the basal metabolic rate and therefore the shorter their lifespan, although there are exceptions to this rule such as the naked mole rat. Smaller animals have a higher surface-to-volume ratio. Or, in other words, a relatively larger area for heat loss to the environment per unit time.