Physical Activity and Obesity

Obesity is a major risk factor for development of type two diabetes. An inactive lifestyle also predisposes for type two diabetes and both physical activity and obesity are therefore, important topics in relation to prevention of type two diabetes. 

1)Explain health benefits of being physically active.

2)Describe how physical training affects energy balance and metabolic health and discuss the
potential of physical training in prevention and treatment of obesity and diabetes.

3)Demonstrate methods that can be used to evaluate physical fitness, body fat distribution and 
    insulin sensitivity. 

Physical activity should preferably be part of a healthy lifestyle on a daily basis. Major health agencies like the World Health Organization recommend that adults throughout the week should do at least 150 minutes of moderate intensity or at least 75 minutes of vigorous intensity aerobic physical activity or a combination.

The activity should be performed in bouts of at least 10 minutes duration and preferably be spread on days throughout the week. Additional health benefits can be obtained with a high activity level.

Additionally, muscle strengthening activities should be performed two or more days a week.
Examples of physical activity include dancing, hiking or swimming in leisure time, walking or cycling for transport, occupational activities and daily activities as household chores, games and sports activities. Seniors aged 75 and above are recommended to aim for similar activity level as other adults and in addition to exercises to enhance balance and prevent falls, at least three days per week. When older adults cannot do the recommended amount of physical activity due to health conditions, they should be as physically active as their abilities and conditions allow.


Children and young people up to the age of 18 years should accumulate at least 60 minutes of moderate to vigorous intensity physical activity per day. Activities include games, sports, transportation, chores and many more activities in the context of family, school and community.
At least three times per week, the intensity of the activities should be vigorous and aim at strengthening skeletal muscle and bone.  

Additional physical activity provides additional health benefits.

A practical way of assessing one's activity level is by wearing a pedometer. A number of 10,000 steps has been marketed as a magic number of steps. Walking ten thousand steps per day will most certainly be beneficial to health, but it's difficult to directly relate numbers of steps to minutes of exercise and health benefits as this depends on walking, running speed, body weight and composition, physical fitness and other individual factors. Physical fitness can be evaluated
by a variety of methods. Some are easy to use and cheap, but not very precise. Other methods are more precise,but require special equipment and are not feasible in larger groups of subjects.

A simple way to evaluate physical activity level is by using a questionnaire in which the subject responds to questions about his or her exercise. Examples of such questionnaires are the International Physical Activity Questionnaires, IPAQ and the Recent Physical Activity Questionnaire, RPAQ. The validity of physical activity questionnaires depends heavily on the eagerness of the subject to give an unbiased assessment of his or her physical activity habits. A more objective measure of activity levels can be obtained by activity sensors worn by the subject. A simple, over the counter sensor is a pedometer by which the daily number of steps can be evaluated. An accelerometer is a more sophisticated activity sensor, which can detect movement in several directions.

Accelerometry can be combined with heart rate monitoring and all GPS to increase the ability of the measurement. Lately, detection of heat flux has been included as a parameter for increasing the precision of the activity estimation. Most activity sensors can easily detect simple activities, like walking, jogging and running, but movements during cycling are more difficult to quantify  Detection of swimming activity requires that the sensor is waterproof.

An expensive, but unbiased way to measure physical activity level is by the doubly-labelled water method. The subject is to drink a glass of water labelled with stable isotopes at both the hydrogen and the oxygen atoms. Hydrogen is excreted from the body owner's water, but oxygen is excreted both via water and carbon dioxide. During physical activity, carbon dioxide is produced due to combustion of energy rich substrates. The higher the activity level, the higher the excretion of carbon dioxide. After the initial distribution of labeled water in the body and one to two weeks after drinking the labelled water, urine or saliva samples are taken and analyzed for concentrations of labeled hydrogen and oxygen. So concentration of labeled substances in these fluids reflects the concentration in the water faith of the body. The carbon dioxide excretion and hence, the total energy expenditure can be calculated as the difference between the rate of decline of labeled oxygen and hydrogen. The physical activity level is calculated by subtracting the basal metabolic rate and the thermic effect of food from total energy expenditure.

Physical performance can be assessed by testing the subject in a gym, the clinic or the laboratory. Many simple tests exist. For example, for determination of walking speed, hand grip strength or balance. The state of the art test for assessment of physical fitness is quantification of maximum oxygen uptake by indirect calorimetry during a biking or running test to exhaustion. During physical exercise, skeletal muscles require energy to contract. The main substrates expended during exercise are fat and carbohydrates, but a small amount of protein is also used. At low exercise intensity, the main substrate used is fat either from intramyocellular lipidstores or supplied by the blood. Blood lipids are either  triacylglycerol from the liver or the gastrointestinal tract or free fatty acids derived from adipose tissue stores. At an exercise intensity of approximately 40 to 50% of maximal oxygen uptake, fat oxidation reaches its maximum rate. As exercise intensity increases, more energy is needed in the contracting muscles.

At higher exercise intensities, less fat and more carbohydrate will supply the energy for muscle contractions. Carbohydrates are derived from skeletal muscle glycogen stores or provided by the blood as glucose. Blood glucose stems from liver glycogen stores or from the gastrointestinal tract after carbohydrate containing drink or meal. Body glycogen stores are limited and when exercise time is increased, less and less glucose and more and more fat will be used. The energy stored in fat can only be released aerobically, meaning by use of oxygen for combustion. In contrast, glucose can be degraded both aerobically and anaerobically. Therefore, both fat and carbohydrate can supply the muscles with energy at low exercise intensities when the aerobic demand is low versus high intensities. Mainly glucose is used. When degraded anaerobically, glucose is turned into lactate. At higher exercise intensities, the aerobic demand is increasing and at a certain intensity called the anaerobic or the lactate threshold. Lactate will start to accumulate in the blood. Untrained individuals have a low anaerobic result at approximately 50 to 60% of maximal oxygen uptake, but physical training can increase this. That means that well-trained individuals can sustain a given exercise pace for a longer period of time. At very high exercise intensities and at the onset of exercise, energy is supplied by local muscle stores of keratin phosphate and ATP. These stores contain very limited amount of energy. I will now explain in detail health benefits of being physically active. Physical activity is healthy for young and elderly, slim and obese, healthy and sick. Muscles are meant to be used and if you don't use them, you lose them. Also, the rest of the body will degenerate, if it's not stressed regularly. Physical activity will affect nearly all organ systems of the body and keep you used both in prevention and treatment of a variety of diseases and physical activity prolongs life. Load bearing physical exercise will increase the bone mineral content and reduce the risk of osteoporosis. Also, tendon and skeletal muscle strength will increase after physical exercise. 
Similarly, the heart muscle will become stronger and can hence deliver a higher stroke volume during every heartbeat. This will decrease heart rate, the blood pressure can be lowered by physical exercise. More in hypertensive than in non-hypertensive persons. The plasma concentration of the good lipoprotein, HDL cholesterol is increased. Various the concentration of the bad lipoprotein, LDL cholesterol and triglyceride in blood have decreased. The risk of atherosclerosis is reduced by physical exercise and thereby, the risk of cardiovascular diseases and stroke. Energy is expended during exercise moving the energy balance in a favorable direction for prevention and treatment of obesity. Moreover, insulin sensitivities increased by physical exercise, both acutely and in the long-term and this effect of physical exercise is effective both in preventing and treatment of type two diabetes. Physically fit persons also have a lower
probability of developing some cancers, especially breast and colon. Additionally, physical exercise can increase mood and self-esteem and maybe also libido and reduce the risk for depression.

 

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Health Effects of Lipids Part2

Atherosclerosis

Atherosclerosis involves the gradual narrowing of arteries due to the build-up of plaque. It takes years to develop and happens insidiously without people noticing it. Clinical problems develop when the obstruction is such that blood flow, and thus oxygen supply, cannot meet demands.The low oxygen supply leads to a condition called ischemia, explaining the term ischemic heart disease.Atherosclerosis occurs in many parts of the body. In the heart it may lead to ischemic heart disease, in the brain it may lead to stroke, and in areas outside the brain and heart to peripheral vascular disease also called peripheral artery disease.

Pathogenesis of atherosclerosis

The normal artery contains three layers.The inner layer is called the endothelium or intima and is in direct contact with the blood. The middle layer contains smooth muscle cells that allow blood vessels to expand or contract. The outer layer of arteries is composed mostly of connective tissue. It is commonly thought that a plaque begins to form because the endothelium becomes damaged, possibly because of elevated lipid levels in the blood, high blood pressure, or smoking. The damage causes white blood cells to stick to the endothelium. What happens is that the endothelium produces sticky molecules called adhesion molecules that capture the white blood cells.After adhesion to the endothelium, the white blood cell moves inside the wall of the artery. White blood cells that move into the blood vessel wall include T-cells and macrophages.In the vessel wall, macrophages take up lipid and become foam cells. This causes the vessel wall to gradually thicken as it fills up with lipid. As the atherosclerotic process advances, smooth muscle cells move into the intima and produce molecules such as collagen, that give the inner wall a connective tissue-like appearance.  In advancing lesions, cells die and cell debris including lipids accumulates in the central region of the plaque, called the lipid or necrotic core.It is believed that the lipids that accumulate in the atherosclerotic plaque primarily originate from LDL, which is able to penetrate the wall of the artery and become scavenged by macrophages. In turn, the macrophages become foam cells and start to produce molecules that aggravate the inflammation.

The two key in the initiation of atherosclerosis are 1)Adhesion and infiltration of immune cells into the vascular wall; 2) Entry of LDL particles into the vascular wall and formation of foam cells.The idea that lipids, especially cholesterol, are deposited in atherosclerotic lesions goes back more than 60 years, and led to the suggestion that atherosclerosis may be linked to elevated blood cholesterol. However, in the ensuing years, the hypothesis that high blood cholesterol levels contribute causally to atherosclerosis and CHD (the “lipid hypothesis”)  faced huge skepticism Even today certain groups of individuals remain in denial about the importance of (LDL) cholesterol in atherosclerosis. Within the cardiovascular research community there is a strong consensus about the role of lipids in atherosclerosis, particularly LDL. In addition to the role of lipids, there is near universal recognition for an important role of the immune system and inflammation in the development of atherosclerosis, based on experimental, clinical, and epidemiological studies (the “inflammatory hypothesis”). What is still lacking is the proof that anti-inflammatory drug therapy reduces myocardial infarctions ("heart attack"). 

Most atherosclerotic lesions are stable and do not cause any problems. In those cases, the lipid core is covered by a thick layer of materials typically found in connective tissue forming a so called fibrous cap. However, when the lesion is very inflamed, white blood cells produce molecules that gradually break down the fibrous cap. The thinning of the fibrous cap causes the plaque to become unstable and make it prone to rupture. The rupture of the plaque is very dangerous, as it triggers blood clotting (thrombosis). The blood clot can partially or completely occlude the blood vessel at the site of rupture, or it can be dislodged and travel further to block a blood vessel elsewhere.

 

 

 

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Health Effects of Lipids Part1

Dietary lipids have mainly been connected to heart disease which is also referred to as cardiovascular disease.
What is heart disease and how does it develop? What are the major risk factors for heart disease?
One the risk factors for heart disease is the cholesterol level in the blood. Cholesterol exists in our blood in two forms LDL and HDL.and one needs to be extremely concerned about ones LDL cholesterol level. This is because having high LDL cholesterol  greatly increases one risk to heart disease.
What is interesting about LDL is that it's levels can be changed by altering your diet, what is the impact of  the amount of cholesterol in your diet on your blood cholesterol level? What about consumption of saturated and unsaturated fat?
Trans fat have also been called killer fats., they used to be abundant in frying oil, pastries, fast food, certain margarines and many other processed foods.
Another hot topic is Omega-3 fatty acids numerous claims have been made about these fatty acids, particularly in their relation to heart disease.

Cardiovascular disease and coronary heart disease

Cardiovascular disease (CVD, also called heart disease) is a class of diseases that involve the heart and/or the blood vessels. The most common form of cardiovascular disease is coronary heart disease (CHD), in which the coronary arteries – the blood vessels providing blood to the heart muscle - become narrow and rigid, restricting blood flow to the heart. Coronary heart disease is also called ischemic heart disease. Another common form of cardiovascular disease is stroke, in which the arteries supplying blood to the brain become blocked and blood flow is impaired. Cardiovascular diseases are most often rooted in a process called atherosclerosis. Atherosclerosis describes the build-up of plaque in the walls of arteries, leading to narrowing of the arteries and gradual obstruction of blood flow. Other cardiovascular diseases include heart failure, diseases of the heart muscle (cardiomyopathy), heart valve problems, and arrhythmias.

Ischemic heart disease (a.k.a. coronary heart disease, CHD) is the leading cause of death in high income countries, whereas infections are the major cause of death in low income countries. It is believed that differences in abundance of infectious organisms, hygiene, medical care, and diet are responsible for the difference in death rates between high and low income countries.

Rates of coronary heart disease or ischemic heart disease differ greatly between countries. The age-standardised, disability-adjusted life year (DALY) rates from ischemic heart disease (CHD) by country (per 100,000 inhabitants, the darker the color, the higher the rates). DALY is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death. One DALY represents one lost year of "healthy" life. The sum of these DALYs across the population, or the burden of disease, can be thought of as a measurement of the gap between current health status and an ideal health situation where the entire population lives to an advanced age, free of disease and disability (Definition from WHO). Use of DALY has become increasingly popular in public health. The highest DALY rates for ischemic heart disease are observed in eastern Europe.

The age standardized ischemic heart disease (CHD) death rates per 100,000 individuals. This measure is calculated differently than the DALY but the overall picture it creates is highly similar: highest rates are observed in eastern Europe, whereas the lowest rates are observed in France and Japan.

Trends in deaths from CVD show a striking pattern. In many western and northern European countries, which originally had the highest rates of CVD, there has been a sharp decline in CVD deaths despite the growing prevalence of obesity. The decrease in CVD deaths is accounted for by a huge reduction in deaths from CHD and stroke and is largely explained by improvements in long-term and emergency medical care, combined with decreased smoking in more recent years. Behavioral adjustments towards diets and exercise are unlikely to have importantly contributed towards the decline

In contrast to western countries, there has been a substantial increase in CVD rates in eastern European countries. The extremely high rates of CVD in Eastern Europe have been linked to tobacco use, dietary behaviors, alcohol use and poor medical care

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Gluten Free

How many people shun gluten?
Millions.A YouGov poll last year found that one in ten UK households have at least one supposedly gluten-intolerant member, and that 60% of adults have bought gluten-free products. According to a US survey by the Consumer Reports National Research Centre,
Gluten responsible for obesity, inflammation and a host of  other chronic health conditions.

Since the turn of the century, gluten-free has gone from being an obscure niche to a multimillion-pound enterprise. Supermarkets now stock a vast range of gluten-free products, from gluten-free curry and gluten-free chicken nuggets to gluten-free Easter eggs.

But what exactly is gluten?
It’s the spongy complex of proteins, found in wheat, barley and rye, that gives elasticity to dough and enables it to rise. When flour is moistened and kneaded into dough, two proteins, gliadin and glutenin, join together to form an elastic, microscopic latticework that traps the carbon dioxide produced when yeast ferments,causing dough to inflate. Baking hardens the gluten, which helps the finished product keep its shape. Wheat – and thus gluten – is ubiquitous in the Western diet, and not just in bread, pasta and cakes; it’s a hidden ingredient in thousands of processed products such as ice cream, soy sauce and dressings.
Humans simply don’t have the enzymes to break down gluten, so some peptides (partially digested bits of the protein) remain in the intestine. For most of us, this is insignificant: they are simply eliminated. But for a small minority, it causes coeliac disease: the peptides cross the intestinal barrier, triggering the immune system. White blood cells go on the attack, damaging the intestinal wall. This results in stomach pain, diarrhoea, bloating, fatigue, weight loss and sometimes destruction of the small intestine. Coeliac disease is a serious autoimmune condition which requires the elimination of all wheat, for life. But many others today believe they are allergic, or sensitive, to gluten, and that giving it up improves their health.

Coeliac disease is rare, affecting about 1% of people in developed nations. A small number of others may suffer from allergies or sensitivities. But the vast majority do not react badly to gluten – otherwise wheat would never have become a leading food source. You could get healthier on a gluten-free diet because it might increase your intake of fruit and veg, and reduce consumption of refined carbohydrates such as white bread, pizza and puddings. But such a diet isn’t good for you per se. In fact, if you eat only gluten-free products, you may be short of vitamins, nutrients and fibre; they tend to be heavily processed, and can be loaded with fat and sugar. Gluten-free brown bread has twice as much fat as the normal alternative.
Diet fads and phobias have a long history. Many symptoms blamed on gluten – bloating, fatigue, “brain fog” and lack of “wellbeing” – have, in the past, been blamed on fat, yeast and monosodium glutamate. The current epidemic of self-diagnosed gluten intolerance is based on very little evidence. But there are complicating factors. Coeliac disease is definitely on the rise: US tests show that it has grown from around 0.2% of the population in the early 1950s to 1% today. And a high proportion of sufferers are undiagnosed: in the UK, tests have shown that one in 100 people have the disease, but only one in 800 is diagnosed (it requires a blood test and an endoscopy).Besides, there are also other forms of wheat allergy and sensitivity.

What are those?
There’s a rare wheat allergy, sometimes called baker’s asthma, which causes itching and sneezing. More controversially, there is “non-coeliac gluten sensitivity” or NCGS. Sufferers have coeliac-like symptoms which resolve themselves when they cut out gluten. (But it’s not well understood, very rare, and some scientists question whether it exists at all.) Finally, the NHS suggests that those who suffer from bloating after eating bread should avoid basic supermarket loaves, made using fast-acting yeast and added enzymes. These can cause gas and indigestion, for reasons that are nothing to do with gluten.

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