Endurance training has long been associated with losing fat, but it is not often associated to the dieting by the slimming industry. Why? Because the industry wants to sell you quick fixes: a book you can read and do something consumerist from, a meal substitute you can eat, a low calorie drink you can guzzle, a trimming cycle you can install at home. Also the gym 'industry' as it has become, do not set out to encourage you into doing several hours exercise at a time, partly because they aim to please by making easy to follow, easy to fit in your 'hectic lifestyle', and partly because they want to downsize staffing levels after 7pm at night.
Your lifestyle is basically consumerist and that is maybe bad from many points of view, but it explains why so many people either rebound from commercial diets or don't comply to their regimes. You are looking for a quick fix, a benefit trade off which passes into your modern notion of a reasonable lifestyle which is so hectic and fixated on earning and spending money. Also, the rat-race is really all in a little treadmill: most people become habituated to fairly low risk, low effort cyclical job -home -hobby life styles which are I know myself, difficult to break. Especially when you are at the workplace more than seven or eight hours a day. You need to free up more time for training, and avoid the habituations to being tired after dinner and being sedentary, or doing a burst of exercise and eating rather too late in the evening.
Plenty of people are sedentary, job obsessed, car obsessed and resulting-ly obese. Whether in private or public health care systems, they later in life view heart failure, diabetes, arthritis etc as something which also has a consumer oriented quick fix: drugs and surgery. It costs individuals and nations unbelievable amounts of money to cure the precocious illnesses of the self inflicted.
You, the sporty fatty are not obese but the extra weight you carry is both symptom and causative agent of potential later life diseases such as the three mentioned, plus stroke, plus other heart complaints, wear on joints, bad backs and so on. In fact though some sporty fatties are actually really very fit, they just have an issue with the errors I discussed in the last couple of bloggs. Put simply the wrong training and the the wrong attitude to life's little sweet luxuries. You need to train longer. You need to reorganise your consumer life style and change your attitude to training for a period of up to a year.
Duration is the Key
Why then is "endurance" training important in losing fat then? Endurance: that is training more than an hour per session at medium intensity. The effectiveness is simply one of only a few reasons we evolved to lay down fatty tissue (adipose tissue). We evolved to be able to use fat reserves to move ourselves from areas of depleted food resources to pastures new so to speak, or to evade danger, which in the modern world is the main way these reserves are used outside any conscious slimming regime.
Why fat? Well it is simply a much more compact way of storing energy believe it or not, than storing glucose as the polymeric glycogen. Glycogen must be surrounded by water and has a finite amount of energy per gram. Fat stores nicely, is also useful to the body as 'padding' round harder tissues, and has a far higher calorific value per gram. It is a biochemical compression of energy into a state which is dense though light and self supporting as drops of fat within adipose cells.
As Dr. Atkins and many other researchers rightly pointed out, in the western world the main cause of obesity - large adipose deposits of that compressed energy - is actually a very high carbohydrate diet, in particular sugars and processed carbohydrates and starches in alcoholic beverages.
A little aside then on Herr Doktor Atkins (RIP). "Eskimo" is actually what lower lattitude aboriginal Canadians called Inuit tribes and it means "meat eater" : One thing Atkins was interested in was that these people eat hugely calorific diets fuelled by fat and protein, but very low levels of carbohydrates (in traditional villages still with the original diet). The tribes need to have a very high calorific diet due to the climate and being active in the cold, but in fact they are not obese if kept away from the modern consumer carbo diet. What factors influenced their previously quite low life expectancy (quoted as 45 years for males) is difficult to conclude- there are however signs that older Inuit men live longer and healthier lives than their children when they adopt a western high sugar lifestyle.
Atkins is an interesting diet which I actually found to be very expensive, time consumer and in the end I fully rebounded from it. However if I had persevered or done more training of over an hour, then I could have had a larger benefit. I failed to really get a grip on reintroducing carbohydrates before I then started training much longer 1 to 3 hour sessions and had reverted to a high complex carbo diet to give me energy.
What I was left with was that joke I had made about the Atkins diet, being that you have to cut out beer, cakes and sweets then why not just cut those out and see what happened? That as you should have read lead to my calorie arithmetic - extra intake in 'luxuries' versus extra burn off in training. So in effect I did the calorie counting for you: concentrate on that equation , reducing the one side in the areas you can easily target as 'extra unnecessary' calories versus the key longer duration calorie burns.
Back to endurance, why is it so beneficial to weight loss? Why though, can it take so long to loose weight? Which metabolic processes are involved?
The key factor is that the body switches on two biochemical pathways when we exercise in durations over one hour, and then there is also a nicely synergistic long term anabolic improvement in how much fat we can burn per hour. Firstly when we exercise such that glycogen is depleted at a constant rate, when we come over an hour for most of us, then our bodies start to mobilise fat from adipose tissues, which is a catabolic (break down) pathway. Fat breakdown products (Free Fatty Acids, FFAs) travel slowly into and around the blood stream. Secondly we further catabolise FFAs into smaller fatty acids and then again down into biochemical products which enter further downstream in the normal sugar metabolism cycle (Kreb's Cycle you will remember from school biology)
What is interesting is that we switch this adipose release pathway on after moderate intensity training after this typically one hour barrier (longer in some, shorter in others) but we keep on burning sugars from glycogen. If we train harder, then biochemists found we can actually burn more fat in the muscles but release less from the stores. This is because there are two other smaller stores of fats: one is the background level of blood FFAs, and the other is a small store in the muscle tissues. Further reading in this rather good scientific review article from sports physiologists, if you have a smidgeon of biochem' in your background.
Humans are a bit unique in their metabolism and omnivorous diet ie eating plants and animals. It is difficult to find animal models and unethical really to go doing muscle biopsies under intense training for either animals or human subjects: it hurts and causes bleeding and damage. So we do not yet know exactly when we engage these local stores or FFA from blood. Suffice to say though we know the net effects of endurance training - we mobilise fat stores and burn them off in our muscles.
This process is most efficient for losing weight then when we train at 65-75% max heart rate (as an index for VO2 max, is the maximum rate of oxygen consumption in exercise , or you could say vice versa, but it is easier to measure your pulse than sit on one of those machines with a breathing apparatus and nose plug! Many other people have done this for you as lab rats or proffessional athletes under selection and training efficacy studies) This efficiency is simple arithmetic, minutes x burn per minute and this is why it is so important to come up in two hour training sessions and to avoid your old 'cram it in sweat sessions' of under an hour.
There is then a net shift of fat out of store and into burning, but in a normal healthy diet we are still burning mostly sugar. Maybe the adipose fat is released and burnt a little, but like a kind of slide puzzle it moves to hold up the blood's base FFA level, and moves to replace the local intermuscular triglyceride fat reserves. This is why it is so slow, it is a parallel process alongside glycogen breakdown and glucose metabolism.
Evidence does suggest though that the exercise regime with a calorie controlled diet is the most effective long term means of eliminating fat cells. Fat cells also lie around waiting to be fed when they are emptied. If they are emptied out by a typical "starvation" diet, which just means you eat less calories than your body actually needs even in a sedentary life style, then they often lurk there because they have had a starvation signal to stay alive. After a longer term endurance training schedule, more cells are gone for good: the body has burnt fat and is finding a better balance.
Also another key factor in taking a long term ( 6 to 9 month or more) regime of endurance exercise ,ie 2 hour sessions, several per week, is that you increase your VO2 - your body can burn more calories up with oxygen and go faster, stronger. It is very likely also that this happens hand in hand with the ability to burn a higher proportion of intermuscular fat and FFA from blood, which is all about shifting the slide puzzle forward.
You could then expect a peak weight loss after your VO2 maximises (which will vary greatly and actually for some people training for 6 months, the line will be linear in nature and the max will be at the end point) This has been an arguement for mixed forms of training for many years and is valid for sports people. However for the sporty-fatty your aim is to lose weight and in a modern job - family environment, doing short one hour sessions are wasting your time. There are no doubt some complex training routines which reach a VO2 max for your age and hours put in quicker, but they will all involve shorter high intensity work outs which burn little fat. Also you may just be maximising your ability to burn glucose not the mixture of fats and glucose you burn in longer duration sessions.