Weight Optimization

Physical inactivity and health

Let’s start with a summary from Key Facts from WHO

Physical activity: Key facts

• Insufficient physical activity is one of the leading risk factors for death worldwide.
• Insufficient physical activity is a key risk factor for noncommunicable diseases (NCDs) such as cardiovascular diseases, cancer and diabetes.
• Physical activity has significant health benefits and contributes to preventing NCDs.
• Globally, 1 in 4 adults is not active enough.
• More than 80% of the world's adolescent population is insufficiently physically active.
• Policies to address insufficient physical activity are operational in 56% of WHO Member States.
• WHO Member States have agreed to reduce insufficient physical activity by 10% by 2025.

Definition

The same WHO website gives us a definition: 

"WHO defines physical activity as any bodily movement produced by skeletal muscles that requires energy expenditure – including activities undertaken while working, playing, carrying out household chores, travelling, and engaging in recreational pursuits.

The term "physical activity" should not be confused with "exercise", which is a subcategory of physical activity that is planned, structured, repetitive, and aims to improve or maintain one or more components of physical fitness. Beyond exercise, any other physical activity that is done during leisure time, for transport to get to and from places, or as part of a person’s work, has a health benefit. Further, both moderate- and vigorous-intensity physical activity improve health."

A website from Harvard Health Measuring Physical Activity gives us a little more information, as in this table:

Measurement.

The measurement of physical activity, hence physical inactivity, is very difficult, as it is for sedentary activity – you can be physically active as well as having long periods of sedentary activity. There are a number of ways of measuring physical activity, as captured by this picture taken from Measurement of Physical Activity & Sedentary Behaviour  - you might also like to look at the definitions included in the website – they include others than the main ones mentioned above, such as ‘Screen Time’.

The website also includes information on the measurement difficulties and requests us to consider:

Reliability: reflects the stability of the tool to measure the same concept over time (i.e., vigorous physical activity).
Validity: describes how well the measurement tool assesses what it is intended to assess.

There may be special measurement tools for various population or clinical subgroups, such as in Assessing physical activity in people with mental illness: 23-country reliability and validity of the simple physical activity questionnaire (SIMPAQ) 

Applicability. Of course, most of these measurement methods are not available in clinical practice, wherever you are, or even for research purposes.

Phone app. Many of us have smartphones with an app that measures the number of steps taken. The measures need to be interpreted with caution, and vary with the position in which the phone is held, the type of activity being undertaken, and are subject to under-reporting when the phone is not carried.

Size of the problem.

These data are taken from Worldwide trends in insufficient physical activity from 2001 to 2016: a pooled analysis of 358 population-based surveys with 1·9 million participants. 

“Prevalence in 2016 was more than twice as high in high-income countries (36·8%, 35·0-38·0) as in low-income countries (16·2%, 14·2-17·9), and insufficient activity has increased in high-income countries over time (31·6%, 27·1-37·2, in 2001). INTERPRETATION: If current trends continue, the 2025 global physical activity target (a 10% relative reduction in insufficient physical activity) will not be met. Policies to increase population levels of physical activity need to be prioritised and scaled up urgently.”

Another estimate comes from: Effect of physical inactivity on major non-communicable diseases worldwide: an analysis of burden of disease and life expectancy

“Worldwide, we estimate that physical inactivity causes 6% (ranging from 3·2% in southeast Asia to 7·8% in the eastern Mediterranean region) of the burden of disease from coronary heart disease, 7% (3·9–9·6) of type 2 diabetes, 10% (5·6–14·1) of breast cancer, and 10% (5·7–13·8) of colon cancer. Inactivity causes 9% (range 5·1–12·5) of premature mortality, or more than 5·3 million of the 57 million deaths that occurred worldwide in 2008. If inactivity were not eliminated, but decreased instead by 10% or 25%, more than 533 000 and more than 1·3 million deaths, respectively, could be averted every year. We estimated that elimination of physical inactivity would increase the life expectancy of the world's population by 0·68 (range 0·41–0·95) years.”

Chronic Disease Control Priorities, DCP3, has a section on Physical Activity.  Amongst a great deal of valuable information that you can see there is the statement: “Economic analyses conducted in a variety of countries indicate that between 3 percent and 6 percent of national health care costs are attributable to physical inactivity.”

In The economic costs of a more physically active population, the RAND Corporation highlights that physical inactivity is associated with not only a cost-of-illness economic burden on national healthcare systems but also a loss in employee productivity. Their model predicts that if every adult on the planet met the recommended 150 minutes of moderate-intensity physical activity per week then there would be a mean global GDP gain of 170 billion US$ by 2025 and 380 billion US$ by 2050.

The economic costs are backed up here:

The economic burden of physical inactivity: a global analysis of major non-communicable diseases 

"Conservatively estimated, physical inactivity cost healthcare systems international $ (INT$) 53·8 billion worldwide in 2013, of which $31·2 billion was paid by the public sector, $12·9 billion by the private sector, and $9·7 billion by households. In addition, physical inactivity-related deaths contribute to $13·7 billion in productivity losses, and physical inactivity was responsible for 13·4 million Disability Adjusted Life Years worldwide."

Causes of physical inactivity

In Physical Inactivity: a global public health problem WHO states:

“The current levels of physical inactivity are partly due to people being less active during leisure time and an increase in sedentary behaviour during occupational and recreational activities. Also, a decline in walking and cycling in favor of using motor vehicles as well as a change in the urban design of towns and cities has been associated with declining physical activity levels. Increased urbanization has resulted in several environmental factors which may discourage participation in physical activity such as:

• violence,
• high-density traffic,
• low air quality, pollution,
• lack of parks, sidewalks and sports/recreation facilities.”

Health risks from physical inactivity

We will discuss the benefits of exercise to increase levels of physical activity later in this course. Physical inactivity has been linked to many major chronic diseases, including cardiovascular disease, diabetes, respiratory disease, cancer, mental illness, arthritis and dementia. Much of the evidence relates to cardiovascular disease- as from DCP3 above: “Physical inactivity causes an estimated 9 percent of premature mortality from all causes, or between 3.1 million (Lim and others 2013) and 5.3 million (Lee and others 2012) premature deaths worldwide in 2010. Inactivity accounts for 6 percent of coronary artery disease, 7 percent of type 2 diabetes, 10 percent of breast cancers, and 10 percent of colon cancers (Lee and others 2012). Although eliminating physical inactivity would have the largest effect on colon cancer (due to a higher hazards ratio), it would avert the largest number of cases of coronary artery disease (due to higher incidence). These estimates are viewed as conservative because of the limitations of using self-reported measures of exposure.”

The paper Systematic review of the prospective association of daily step counts with risk of mortality, cardiovascular disease, and dysglycemia concludes "Evidence from longitudinal data consistently demonstrated that walking an additional 1000 steps per day can help lower the risk of all-cause mortality, and CVD morbidity and mortality in adults, and that health benefits are present below 10,000 steps per day."

However, the risks extend beyond cardiovascular disease. Here are some data from the risks of 5 diseases: Physical activity and risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke events: systematic review and dose-response meta-analysis for the Global Burden of Disease Study 2013 

“In conclusion, the findings of this study showed that a higher level of total physical activity is strongly associated with a lower risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke, with most health gains occurring at a total activity level of 3000-4000 MET minutes/week. Results suggest that total physical activity needs to be several times higher than the recommended minimum level of 600 MET minutes/week for larger reductions in the risk of these diseases.”

An example of the difficulty of obtaining good risk data comes from this large study which needed to combine studies of nearly half a million people Physical inactivity, cardiometabolic disease, and risk of dementia: an individual-participant meta-analysis .  You will see from the figure from that paper, that while the risk of cardiometabolic disease was confirmed, there did not appear to be a risk of physical inactivity on dementia.

In a link to Physical Activity and Cancer we see that “There is strong evidence that higher levels of physical activity are linked to lower risk of several types of cancer” - these include bladder, breast, colon, endometrial, oesphageal, renal and gastric cancer.

The paper which we have met before, Assessing physical activity in people with mental illness: 23-country reliability and validity of the simple physical activity questionnaire (SIMPAQ) states: “Physical inactivity is a key contributor to the global burden of disease and disproportionately impacts the wellbeing of people experiencing mental illness.”

Physical Activity and Incident Depression: A Meta-Analysis of Prospective Cohort Studies  reports a large prospective study which concluded: “Available evidence supports the notion that physical activity can confer protection against the emergence of depression regardless of age and geographical region”

Physical activity, exercise and immune function - a fact sheet prepared in response to the Covid-19 pandemic reports on the relationship between physical activity and immunity. The conclusion of the evidence review "is that there is no evidence to indicate that engaging in vigorous-intensity exercise within or even slightly over the recommended guidelines of 150 minutes per week is detrimental to immune function. On the contrary, regular engagement in moderate-to-vigorous physical activity and structured exercise is critical to stimulating the immune system to perform its job effectively."

Interactive body map: physical inactivity and the risks to your health is good fun to explore and provides evidence for the risks for a large number of conditions.

Note: Exercise and Energy Balance

Exercise has been proposed as a strategy to obtain a negative energy balance, resulting in weight loss. However, it is important to note that exercise alone is an inefficient strategy compared to caloric restriction. The table below outlines the average energy expenditure of common activities compared to the average energy yield from common foods.

Physical Activity (kcal per 30 minutes*)	Food (kcal)
Sleeping (23 kcal)	Small Apple (32 kcal)
Watching TV (28 kcal)	Small Banana (52 kcal)
Weight-Lifting (112 kcal)	35g Serving Kellogg’s Coco Pops (136 kcal)
Walking 3.5mph (149 kcal)	50g Basmati Rice (175 kcal)
Soccer/Tennis (260 kcal)	1 98g Bagel (245 kcal)
Running 6mph (372 kcal)	Prezzo Spaghetti Bolognese (653 kcal)
Swimming: Front Crawl (409 kcal)	9-10 Inch Small Pizza (864 kcal)

*for a 70kg adult

Adapted from Harvard Medical School and NHS calorie checker.

2. Exercise and Mental Health

Exercise also promises to be a cost-effective supporting strategy for patients with mental illness. The benefits range from improvements in mood and cognitive function to reducing anxiety and depression. Read this letter to the editor to better understand the effects of exercise on mental health.