Exercise is good for you. As the saying goes, “tell me something I don’t know”.
As a young kid, I was never into exercise or sports. I LOVED to play so whenever I could, I was certainly active.
I think it was around age 16 when I started to make a conscious effort to include more physical activity, a.k.a. exercise. That’s when I began my lifeguarding courses and training. I started with the Bronze Medallion, then the Bronze Cross, onto the Award of Merit and finally the National Lifeguarding-Lifesaving Society certification.
Before this, I wasn’t physically fit because I never engaged in regular exercise but I did once I started my lifeguard training; swimming, swimming skills and heaps of time trials were an integral part of the courses. After all, I had to be ‘in shape’ enough to swim out and rescue someone if need be.
Fast forward to today, a few decades later, and I can’t imagine my life without some kind of physical activity/exercise which research continues to justify.
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Is a workout good medicine?
In a nutshell, people who exercise tend to live longer, healthier lives. It’s been known for decades that activity lowers blood pressure, reduces the risk for diabetes and stroke, improves mood, etc but we haven’t really understood how exercise accounts for ALL of the observed benefits.
To date, most of the research has taken a macro viewpoint. As mentioned above, it’s looked at through the lens of traditional risk factors of chronic diseases like cholesterol, blood pressure, weight management and more but exercise’s protective impact is much more nuanced.
SIDE NOTE: in this post, exercise, activity and physical activity will be used interchangably although many have an negative association with the word “exercise” because it conjures up images of the gym which can be intimidating.
As with other medical research, exercise physiologists and others are examining physical activity’s role in modifying gene expression, how it influences different tissues and organs’ use of glucose, its role in anti/inflammation, oxidation defenses, mitochondrial function, and even exercise’s impact on immune function.
Whatever the reason, exercise is good medicine and not only that, research continues to underscore just how potent exercise is when it comes to preventing chronic disease, as well, treating and managing it.
Health benefits of exercise
Exercise benefits your whole body and not just certain parts. Many think that ‘cardio’ or aerobic activity like jogging, swimming, cycling, etc are primarily good for the heart and lungs, a.k.a. the cardiorespiratory system. On the other hand, resistance or weight training is considered to be all about the muscles.
The good news is, it’s waaaaaaaay better than that.
Exercise DOES benefit your heart and lungs and your muscles but it positively modulates your immune system, improves metabolism (that’s all the biochemical reactions/processes that enable life, NOT just ‘burning calories for weight management’), and it affects your very DNA. We are on the cusp of seeing exercise for what it really is, a form of medicine that needs to be ‘prescribed’ along with other interventions as needed.
Your brain is amazing. It’s considered the most complex structure in the known universe.
The adult human brain weighs about 1.3 to 1.4 kg (or about 3 pounds) yet it has a huge need for energy. It accounts for about 25% of your body’s energy consumption; it short, it’s an energy hog. Your noggin is sensitive to what you eat and drink. Your brain health is affected by alcohol, as well as, other foods that can harm brain function.
The good news is, a healthy diet AND regular exercise do just the opposite. Because your brain is quite literally enmeshed with a seemingly never-ending network of blood vessels, keeping them smooth, clear of debris, and flexible is the foundation to good brain health and function. And exercise is known to do just that.
Being active helps to make your blood vessels bigger and to work optimally. When there’s good blood flow, oxygen and nutrients can reach your neurons (brain cells) better and waste products like CO2 and other metabolic byproducts can be removed. Better blood flow is also associated with less cognitive decline and dementia.
But there’s more. Like other parts of your body, your brain cells need to have good metabolic health. This means that your brain can develop insulin resistance just as your liver and muscles can. Being able to respond to insulin and to take up glucose is crucial for energy production within your neurons. It’s for this reason that the term “Type 3 diabetes” was coined around 2005.
Insulin resistance in the brain is associated with increased dementia including Alzheimer’s disease. Turns out cardiovascular fitness, metabolic health, insulin, and glucose metabolism is front and center where your cerebral health is concerned.
To put this in perspective, a study set out to determine if high-intensity interval training (HIIT) would increase brain metabolism (improve uptake and use of blood glucose) in both younger (18 to 30 years) and older adults (65 to 80 years).
Each participant’s brain glucose uptake was measured before and after HIIT and was also compared to a time when all of them were sedentary (as part of a larger study design).
Amazingly, glucose uptake increased significantly after 12 weeks of HIIT compared to the sedentary period. Specifically, glucose uptake increased in brain regions (parietal-temporal and caudate) where it’s reduced in Alzheimer’s disease. This is interesting because aging brains lose their ability to use glucose and as a result, brain cell energy production declines leading to neuronal dysfunction; a hallmark of dementia (1).
On a side note, this is why there is great promise with a ketogenic diet. Ketones don’t need to be transported into brain cells like glucose does so there’s never any ketone-resistance, AND the brain can easily and loves to use, ketones as a fuel source. In fact, when ketones are available, they’re the preferred fuel.
Research in this area has demonstrated how a ketogenic diet can possibly benefit those with dementia – stay tuned (2).
Check out this Youtube presentation – Can Ketosis Slow Alzheimer’s Disease? – by Stephen Cunnane
Similar effects with HIIT are seen in Parkinson’s disease. A so-called bout of acute (short term) exercise resulted in increased activity areas of the brain that normally less active in Parkinson’s (3).
Muscles and metabolic health
Whether your lifting weights or something more aerobic, exercise builds and maintains muscle. Exercise (along with dietary protein) literally stimulates your genes to build more muscle. Most probably think of improved strength when they think of bigger muscles and they’re right but of course, you knew there’s more to the story.
When it comes to your overall health, having more muscle means less diabetes risk, and exercise enhances your immune function. Better immunity means less risk for colds and flu and complications from them and a fitter cancer-fighting white blood cell army.
When it comes to metabolic health, having more muscle mass that’s very insulin sensitive means you have a larger repository to handle the glucose that ultimately enters your bloodstream from the digestion of dietary carbohydrate.
More muscle also means quicker removal of sugar from your bloodstream. While this makes sense for those with elevated blood sugar as seen with prediabetes/insulin resistance (fasting blood sugar > 6.1 mmol or 100 – 125 mg/dL, or an AIC > 6.5) or those with diabetes, it also applies to those without these diagnoses.
Whether it’s chronically elevated blood sugar levels as seen in prediabetes and diabetes or just having periodic higher blood sugar for a few hours after eating over the course of the day, blood sugar and the corresponding insulin spikes that come with dietary carbohydrate takes its toll over the decades. It contributes to microinflammation and glycation.
Having and maintaining insulin-sensitive muscle is good medicine when it comes to dealing with this.
PRO TIP: did you know that nothing does more to improve whole-body insulin sensitivity than a single bout of exercise? No medication can boast that; never has, never will.
One of the theories of aging looks at the impact of age-related mitochondrial decline. Mitochondrion are structures within cells in which the biochemical processes of respiration and energy production occur. They are the site where the energy that’s released from the digestion of food is turned into energy molecules called ATP. ATP gives your cells the energy they need to do their respective jobs.
While most cells have them, cells with high energy needs HAVE tons of them. For example, it’s estimated that there are between 1000 – 2000 mitochondria per liver cell whereas your heart has about 5000 per cell. The muscle cells of your biceps, that don’t have the same energy demand 24/7, only have about 200 mitochondria each.
FUN FACT: There are about 10 million billion (or 100, 000 trillion) mitochondria in an adult human
So, anything that can help to slow down mitochondrial loss that’s inevitably seen with aging is a good thing. When your mitochondria lose function, they’re unable to “burn off” all the cellular fuel they get from the food you eat which leads to cell damage including damage to your cells’ DNA.
A study in healthy young 18-30-year-olds that looked at the impact of 8 weeks of combined training (resistance and endurance) on mitochondrial function found that combined training was better than endurance or resistance training alone. In terms of specifics, exercise increased oxidative capacity (meaning the mitochondria increased their capacity to work harder).
Exercise also increased the amount of mitochondria proteins that are used to burn food energy (fuel). There was also increased mitochondrial transcription factors (translation, exercise stimulated muscle cells to produce more mitochondria !) (4, 5).
In other words, exercise has a potent anti-aging effect on the life of your cells’ energy units, your mitochondrion. Being active boosted the efficiency of their ability to create energy and exercise stimulated the production of more mitochondria forestalling the decline seen in older adults.
Exercise fits your genes
While casual exercise, a few hours a week or 2 or 3 spin classes, etc has never been shown to result in meaningful weight loss by burning enough calories without some kind of calorie reduction, it’s not without its merits.
Exercise DOES have potent and far-reaching benefits from improving mood, reducing stress, lowering blood pressure and more, and as stated above, improving and maintaining insulin sensitivity. So while exercise isn’t the best strategy to help you fit into your jeans, exercise does fit your genes’ needs in other ways.
We’ve been told for decades that prediabetes and diabetes are the results of not exercising enough and eating too much, leading to weight gain. In turn, it’s believed that weight gain leads to insulin resistance but the evidence suggests that it’s not that linear.
There is evidence that some degree of insulin resistance precedes weight gain and this is where exercise and your genes come in. We know exercise builds bigger muscles, however, exercised muscle, while historically never seen as a metabolic player beyond its role as a bank account for excess blood sugar, releases signaling molecules into your bloodstream.
Many of these molecules regulate muscle growth, nutrient metabolism, inflammation, AND influence insulin sensitivity (6, 7, 8). One of these muscle-derived signaling molecules called myokines communicates with other organs including the liver, gut, pancreas, adipose tissue (body fat including visceral fat, the fat within your abdominal cavity that surrounds your organs) and more.
Having nothing to do with burning calories, weight loss and preventing weight gain, exercise plays a much more nuanced role in metabolic health that goes beyond weight by literally, positively modulating the genes involved in these interconnected physiological pathways.
Exercise is also your best friend when it comes to inflammation.
Because exercise improves insulin sensitivity and can help with weight loss when coupled with a modest calorie reduction, it can help to prevent the accumulation of the most problematic type of fat; abdominal or visceral fat.
Abdominal fat is very metabolically active. It’s known to produce pro-inflammatory cytokines (proteins) that drive systemic (whole-body) inflammation as well. We used to think that fat cells were just storage sites, a place to deposit excess calories/energy but today we know adipose is very busy.
The cytokines that fat pumps out enter the bloodstream which circulates throughout the body, ultimately causing havoc. Chronic inflammation is associated with increased risk of many diseases of old age and, in turn, chronic disease drives inflammation – the ultimate vicious circle.
A sedentary lifestyle that’s low or devoid of physical activity and decreased insulin sensitivity and the insidious accumulation of abdominal fat (increased inflammation) that typically accompanies older age increases your risk for lots of different diseases and disorders (9).
Case in point, a study that looked at the impact of decreased activity (in this case walking) on insulin sensitivity and abdominal fat accumulation, researchers found that going from 10,000 steps per day (active) down to 1,500 resulted in reduced insulin sensitivity (a.k.a increased insulin resistance) and a 7% increase in abdominal fat mass after just 2 weeks.
As of now, there’s no official dose of exercise to give as a prescription to treat various ailments such as high blood pressure, osteoporosis, depression, prediabetes or diabetes, etc.
Whether you call it “exercise” or “physical activity”, moving your body and moving it often is just good medicine. Beyond the generic advice to ‘exercise more’, health professionals really should be seeing activity as a legit treatment like medical nutrition therapy or medications.
This has been shown time and time again.
When comparing standard care (medication and diet teaching) to an intensive lifestyle intervention in 64 adults with Type 2 diabetes, 74% of those in the exercise group were able to stop taking their diabetes medication within a year of starting the program (10).
A review of 300 randomized controlled trials (considered the gold standard) that compared the effectiveness of exercise versus medication interventions on mortality outcomes (death) in those with diabetes and heart disease, exercise proved more effective (11).
I suspect, deep down, everyone knows this. Given that medications typically interfere with one aspect of a metabolic pathway to affect a result, e.g. lower blood sugar or blood pressure, pharmaceuticals simply can’t match or compete with, the whole body, whole metabolism impact that exercise has.
In a perfect world, it would be great to prescribe a certain type of exercise, with a certain effort for a certain length of time and frequency. Whether or not future studies bring that to bear is yet to be seen.
In the meantime, there’s no reason to wait. General guidelines are to get a minimum of 150 minutes of purposeful activity per week. This works out to 2.5 hours in total. It’s best to spread that out over the course of the week if you can rather than jamming it in over the weekend for example.
You can’t store fitness so if you can do something, anything, frequently – the better. Try not to go longer than 48 hours without doing something. At an appropriate pace, try to increase the intensity over time. Getting more than the minimum will help to improve your fitness and give you more of the benefits.
Even better is any activity that you enjoy that gets your heart and breathing rate up, and as studies show, it’s best to get a combination of endurance (“cardio”/”aerobic”) and resistance exercise.
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Doug Cook RDN is a Toronto based integrative and functional nutritionist and dietitian with a focus on digestive, gut, and mental health. Follow me on Facebook, Instagram and Twitter.