The Truth About Obesity
Chris Bavin discovers what science can tell us about why 2/3 of us are overweight - and how we can fight it.Read Article
A science documentary series tackling everyday issues that affect us all. Each episode features different presenters and experts in their fields.
The Truth About... was broadcast on Wednesdays at 9pm on BBC One for three weeks from 6 January 2021. To find out more or to watch on BBC iPlayer head to the BBC programme pages .
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The immune system has evolved to protect us against infectious agents, including viruses. This article is a general introduction to these areas.
Currently, with the ongoing Covid-19 pandemic, there is great interest in exactly how the immune system protects against viruses and the development of anti-viral vaccines.
Viruses infect cells and take over the cell’s molecular machinery in order to replicate and spread. The immune response against viruses has two main components:
1. preventing cells becoming infected
2. recognition and destruction of virus-infected cells.
These two elements are carried out by different arms of the immune system. Antibodies are effective in limiting the spread of virus between cells in blood and body fluids. They can also prevent viruses from entering and infecting cells. Once a cell has become infected some of the cells of the immune system can recognise the infected cell and destroy it before viral replication is complete. The cells responsible for recognising and destroying infected cells are T-lymphocytes (T cells) and another type of lymphocyte, Natural Killer cells (NK cells). The relative importance of antibodies and lymphocytes in eliminating the virus depends on which virus is involved.
The basis of immunity to an infection is that the immune system specifically recognises an infectious agent that it has encountered and remembers it, so it can mount a faster and more effective response if it is encountered again. In the months immediately following a viral infection, assuming that the virus has been eliminated, antibodies against that virus will gradually decline. However, more important is that the numbers of cells that produce those antibodies (B cells) and the T cells that recognise virus-infected cells have increased enormously. Consequently, a subsequent encounter with the same infectious agent will be much more effective. It is important to understand that long-term immunity to infection is primarily dependent on this expanded population of long-lived ‘memory cells’, with a gradually declining contribution from antibodies during the first year.
In the case of COVID-19, antibodies against the external spike-protein appear to be most effective in preventing infection. The principle of vaccination is very simple – train the immune system to recognise and react against the infectious agent. Also, a vaccine should stimulate an effective immune response, while being harmless to the person who receives it. Since antibodies (produced by B cells) and T cells specifically recognise components of the virus a vaccine must include some of the virus components. Such a molecule recognised by a B cell or T cell is called an ‘antigen’. When they are activated by antigens in the vaccine, the populations of lymphocytes that recognise virus antigens are expanded and some develop into memory cells. Interestingly, but perhaps unsurprisingly, B cells and T cells recognise antigens in different ways. Antibodies are usually most effective when they bind to the outside of a virus, since they prevent it from binding to and infecting a new cell. In the case of COVID-19, antibodies against the external spike-protein appear to be most effective in preventing infection. In contrast T cells potentially recognise internal or external components of the virus, as they interact with infected cells which have viral antigens presented on their surface.
There are several different ways to produce a vaccine against a virus (Fig.1). Earlier vaccines, used the virus itself but chemically inactivated in such a way that it could not produce an infection. Another route was to develop a variant of the virus that could replicate, but which did not produce any symptoms or pathology in the recipient. The two main types of polio vaccine were derived by these two strategies – inactivation or attenuation.
Fig.1 Five different strategies for producing an anti-viral vaccine. 1. The virus can be attenuated so it retains its antigens and can replicate but is no longer pathogenic. 2. The virus in inactivated chemically. 3. Viral components can be obtained directly from the virus or by genetic engineering and expression of viral proteins. 4. Genes for the critical antigens of the virus are inserted into an innocuous virus which acts as a carrier (vector) of the antigens. 5 Genes for viral antigens (DNA/RNA) are used for direct injection into the recipient.
More recently, vaccines have been developed against individual components of a virus, for example against purified spike-protein of COVID-19. One limitation here is knowing which component(s) of the virus are important for inducing immunity. Also, recall that the antigens which stimulate B cells and T cells are often different. Moreover an immune response to a single virus component is often less strong than the response to an inactivated or attenuated whole virus. For this reason, such antigens may be modified to make them more immunogenic, or to favour one type of immune response.
The latest vaccines are produced by genetic engineering. The idea here is to use the genetic material of the virus, to induce production of viral components which then stimulate the immune response. One strategy for COVID-19 is to take the gene that encodes the spike protein and insert it into a harmless virus. The virus has very limited capacity to replicate, but it still produces the COVID-19 spike-protein which induces specific antibody production. This approach is used by the Oxford/Astra-Zeneca and Russian Sputnik V vaccines. Finally there is one more approach which immunises recipients with the viral antigen gene(s). It relies on the recipient’s cells taking up the gene and expressing it, so that virus antigens (but not virus) are produced by the cells of the body. This approach is relatively new and it is used by the Pfizer/Biontech and Moderna vaccines against COVID-19. Table 1 summarises different types of vaccine which have been developed or are under development for COVID-19.
Vaccines undergo rigorous trials, similar to drugs, before they are released for general use.
Vaccines undergo rigorous trials, similar to drugs, before they are released for general use.Vaccines undergo rigorous trials, similar to drugs, before they are released for general use. The exception to this rule is where an infection is very dangerous or uncontrolled and it is necessary to put a vaccine into the field as quickly as possible. This was seen with Ebola virus in helping control outbreaks of Ebola in the Democratic Republic of Congo and Zaire. Where mortality from a virus infection is high, there is more tolerance of adverse reactions against the vaccine, and the normal extended testing programs can be abbreviated.
A normal testing program is carried out in four phases. The first phase examines basic safety of the vaccine in healthy volunteers. The second phase expands the initial trial to a larger and more diverse group of individuals (older, younger, different ethnic groups, etc.) and the third phase determines whether the vaccine is effective in a large cohort (thousands of people). To determine if a vaccine is effective it has to protect people from the naturally occurring infection and if the prevalence of infection is low in the community, then it takes longer to see whether the vaccine is effective. Due to the urgency to develop vaccines against COVID-19, volunteers were recruited as quickly as possible and where possible phase 1-3 trials have been overlapped to reduce the time before results became available. Phase-4 trials look for any long-term effects of the treatment and extend, of necessity, over many years.
It is important to note that any particular vaccine may not be ‘best’ for all people. Take for example a live attenuated polio virus vaccine. It works well in most people and is very safe, but in individuals whose immune system is suppressed, they may not control the vaccine strain of virus so well. For these individuals an inactivated vaccine is better.
All of the approved COVID-19 vaccines have been tested in real-world trials and found to be very effective. But notice that these trials are not exactly comparable, because different trials took place at different times and in different countries where the dominant strains of the COVID-19 virus have been different. For this reason, a simple comparison of ‘vaccine effectiveness’ in these trials does not tell us if one vaccine is truly more effective than another.
Vaccine test tubes in lab
Some vaccines are astonishingly effective. The measles vaccine is 97% effective and has not required any substantial modification for many years. The effectiveness of flu vaccine is variable from year to year as new strains emerge and new vaccines are developed annually; to date no effective vaccine for HIV has been developed. In these examples the key difference is the stability of the virus. Viruses can mutate to evade immune responses and HIV and flu are very good at changing their genetic make-up, so they are no longer recognised effectively by the immune system. We do know that COVID-19 is more stable than flu or HIV, although many different strains have emerged already. In at least four cases COVID-19 ‘variants of concern’ have emerged that increase the rate at which the virus spreads – These are the strains originally noted as spreading in the UK (Alpha), South Africa (Beta), Brazil (Gamma) and India (Delta). Some of these variants can partially evade the antibodies produced either by a vaccination or a natural infection. The reduced immunity is due to mutations in parts of the spike protein recognised by antibodies. However since the antibodies in different individuals recognise different parts of the spike protein, some vaccinated people will be less well protected against variants than the original COVID-19 strain, while others will be just as well protected. This variation in protection is due to the variation in the immune responses in different people.
Viruses that can evade immune responses are at a selective advantage, but a virus cannot mutate indiscriminately – if the virus loses its ability to infect cells then it can no longer spread. Antibodies directed against critical areas of the virus that are required for its infectivity are therefore likely to be most effective against different strains.
Another consideration is the type of immune response that the infection or vaccine induces. In some cases, immunological memory lasts for very many years, in other cases only a few years. We are not yet sure how long natural or induced immunity to COVID-19 will last, but we can predict that it will depend on memory cells, not just on antibodies.
We can also consider how different types of vaccine may be more or less effective in producing long-lasting immunity. Inactivated and attenuated virus vaccines contain many viral proteins so they can induce a wide range of antibody and T cell responses. This may be important if a virus mutates one of its antigens and evades an immune response. In this case there may still be effective responses to other antigens or other parts of the mutated antigen. One advantage of the new mRNA and vector vaccines is that they can be modified relatively quickly; if a new strain of virus is detected the sequence can be determined quickly and the sequence of the mRNA in the vaccine, or the gene in the vector, changed accordingly. Hence each type of vaccine can have its own advantages.
I am often asked. ‘Is Covid-19 here to stay, and do we just get used to living with it?’ Previous major pandemics, such as the 1919 influenza pandemic circulated for several years before a high level of immunity developed in the population following natural infection. As time passed, the severity of the disease declined as some of the immunity against the original strain was partially effective against later strains. It is interesting therefore that none of the new variants of COVID-19 have been able to completely escape the immune response to the original (vaccine) strain of the virus. If COVID-19 follows a similar pattern to previous pandemics, the disease may indeed be with us indefinitely, but could decline in severity as immunity builds up, both in individuals and in the population. It may however be necessary to provide annual booster vaccinations against emerging strains, just as we currently do for influenza.
Due to the Covid-19 pandemic many people have turned to getting fit at home, but the distractions can be challenging! Candice Lingam-Willgoss gives you five tips to keep you motivated...
This works on the same principle as you going to the gym or an exercise class. When you go to the gym you are sub-consciously shifting your mindset into exercise mode and this is the same type of feeling you need to recreate at home. That may mean that you convert the spare bedroom or a corner of the garage into your workout space, so that when you enter that space you know it is time to work out and get you into the zone . Similarly, setting clear times to workout can help you stay on track, for example you may have been used to going to a class at the gym in your lunchbreak, in which case set aside the same time slot to complete your session. Try to avoid distractions in this space so that you are able to focus on your exercise. This approach strives to manage the environment and ultimately provide more opportunity to exercise.
This is an interesting point as there are two sides to this tip. Firstly, it is important to wear the right type of clothes to exercise, for example correct trainers and clothing that allows you to move and complete your workout in a comfortable manner. But this also relates to making you feel a certain way. You might like to buy some new clothing as this can suggest a new beginning and give you a new identity, as the trigger of wearing the right kit can make you feel like an exerciser and tap into your subconscious giving you that added motivation.
Music has been found to shift emotional and mental states. It is good to put together a workout playlist of tracks that you wouldn’t normally listen to, as similar to tip 1, having the right music playing can shift your mindset from being sedentary to becoming an exerciser, and if you choose the right music it can help to psych you up ready to work hard – just think of the impact of ‘Eye of the Tiger’ in the Rocky films! You may like to have a listen to our OU sport and fitness playlist for some added inspiration.
Goal setting is perhaps one of the most popular techniques that can be used to keep people motivated and support behaviour change. Goals can allow you to have focus within your sessions and track your progress, but it is important that goals are varied and set appropriately. You may decide to have a longer-term goal perhaps of losing weight or being able to perform a certain exercise at a higher intensity, but you will also need shorter-term goals that help you achieve these longer-term goals. These shorter process or performance-driven goals are usually largely in your control and tend to help most with adherence, for example to complete four workouts a week or to increase the number of press ups you do each session. These types of goals allow you to feel successful and help prolong motivation. What is perhaps most important though is to write them down and make sure you can see them clearly, so stick them up on the fridge or on the mirror, somewhere you will see them daily to give you that boost.
Variety within your exercise routine is essential if boredom is to be avoided. A good idea is to start with a 4-week plan that allows you to change around your weekly routine. You can add in an assortment of training types such as weight training, High intensity training, core strengthening or even an online class. Keeping this varied will not only keep you interested and focused but also ensure you are training all aspects of your body, benefitting your overall fitness.
What is most important though is to have fun. There is a type of exercise out there that will suit everyone, it is just finding what you enjoy, whether it’s jumping on the exercise bike in your back bedroom, lifting weights or dance, hopefully these five tips will help you to find exercise that you enjoy and can start to look forward. While the rewards of exercise may seem like they take a long time to come there are few things better than the warm, relaxing feeling that comes in the hours after exercise. You will likely feel that you have more energy and will sleep better, and you will also get the chance to feel better about yourself.
Dr Sharon Mallon explores what is meant by self-care before introducing you to some of the top inexpensive and time-effective ways that you can introduce self-care practices into your life.
Self-care is a concept that has been gaining further momentum over the past decade. However, it is a term that has gained new meaning in 2020; a year in which the COVID-19 pandemic has upended many aspects of our lives, disrupting how we live and work on a day-to-day basis, while also impacting on how we perceive the future. In combination, these circumstances have brought a unique set of challenges to our mental health and wellbeing.
Whether you know it or not, you already engage in a range of self-care practices that are designed to protect your physical health. For example, one of the most common self-care routines that we all should have is the twice-daily brushing of our teeth to help protect them against tooth decay. In relation to mental health, it is a term that originally emerged in the academic literature in relation to social workers, therapists and other professionals who work in environments where they were exposed to emotionally taxing work. Here, it was used as a way to encourage these workers to develop practices that would help them to protect their mental health and wellbeing, allowing them to avoid emotional exhaustion and burn-out. Over time, knowledge gained from these professions, combined with broader shifts in our understanding of mental ill health, have meant that self-care practices have become widely acknowledged as being critical to all of us, helping to protect us from mental ill health.
But what exactly do we mean by self-care and what does it look like in practice? Although this may seem obvious for maintaining mental health, it is something we can all be prone to forgetting to do, especially as we struggle to cope with the changes and uncertainties of life, including caring responsibilities or work demands which make time for ourselves limited.
Self-care activities allow us to take time out of our usual routine to nurture ourselves, to comfort ourselves, and to provide space to reflect on our own thoughts, all of which will allow us to maintain a sense of equilibrium that will ensure we stay well enough to take care of others. Or to put it another way, self-care activities can allow us to find a balance between the demands that are placed on us, such as taking care of children, keeping up with the food shopping, actively listening to a friend who is upset and managing a stressful situation at work. In short, all the things that may cause us suffering or stress, and the actions we take to ensure that we don’t burn out or over stretch ourselves in ways that may make us unwell.
As we are all individuals, the things that offer us moments of calm and psychological nourishment vary, and as a result our self-care practices will vary. The most important thing is to think about the things that help you to find balance and to think about what the goals and objectives are for your self-care routine, as this will help you to select those activities that will be most beneficial to you.
Here are some top tips for things that may help get you started.
Plan to do one activity a day that makes you feel joyful.
This might be watching a comedy, singing an uplifting song, going for a walk or having a bath. Whatever it is, however small, make time for it every day. Make planning this small piece of joy as routine to you as cleaning your teeth, brushing your hair or washing your face.
Daily exercise, even very mild exercise such as an outdoor walk, has been linked to improved mental health. Movement in your body can stimulate the senses and help to shift your thoughts away from repetitive or negative patterns and can also dissipate stress hormones.
Seek out new experiences, new knowledge or new activities that can give you a renewed sense of confidence or accomplishment. You might think this will be hard to achieve in a global pandemic, but it could be as easy as exploring a new podcast, for instance.
At the end of each day check in with yourself, ask yourself what you did today that helped you feel a sense of balance and those that impacted negatively on your mood. Then reflect on how you might make this different tomorrow. If it helps do this in a written journal format.
Keep an eye on the nature and tone of your internal dialogue; although we don’t often acknowledge it, the way we ‘talk’ to ourselves can add to our stress and contribute to us feeling that we don’t have a sense of control over what is happening to us. Instead, support yourself through positive self-talk. For example, if you notice that the way you talk to yourself is harsh in terms of tone or words, try instead to be more positive, saying things like ‘I can do this’, ‘I am enough’, ‘ I will get through this’, ‘this time will pass’.
Woman making a heart around the sun
Don’t forget that self-care doesn't have to be complicated. It is simply best understood as activities that offer moments in which your sense of self can be restored, rejuvenated or nourished. At the very core of ‘self-care’ is an acknowledgement that regardless of what is going on in our lives, we have a relationship with ourselves and in order to maintain good mental health, we need to look after this relationship.
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