Andrew Hamilton present further evidence in favour of time-restricted feeding for weight management MORE
Fat burning: how working out in the cold can reduce your fat levels
As the weather gets colder, you may feel like hibernating instead of exercising, but don’t give in – get out and do it! Winter exertions can transform your body into a true fat-burning furnace, making you slimmer and fitter by the time April’s balmy breezes finally blow.
How can cold air clip corpulence from your body? When frosty gusts strike your skin, your brain spurs your adrenal glands into action. The adrenals release surplus quantities of a key hormone called epinephrine (adrenaline), and epinephrine forces your fat cells to push increased amounts of fat into the blood. The fat can be quickly captured and metabolised at a high rate by your muscles.
Activity magnifies this burning of fat, because exercise itself raises epinephrine levels and depletes muscle glycogen. Happily, high-intensity exercise is not required to break down blubber; in fact, top-speed efforts actually tend to thwart fat metabolism. Research suggests that an optimal intensity for fat degradation is about 70% VO2max, i.e., at about 80% of maximal heart rate (or 30 to 45 seconds slower per mile than 10-K race pace for runners), an exertion level which feels fairly comfortable for most individuals. Ignore recommendations you might see in the popular press to exercise more lethargically than this in order to burn more fat; such recommendations are wrong.
Burning the deep, dangerous fat
Even better, winter exercise not only makes a sizeable dent in your fat stores, it also probably helps get rid of your most dangerous fat – the fat which is inside your body cavities, clinging to your internal organs. Strangely enough, it’s this deep, internal fat – not the fat hidden under your skin – which is much more likely to be related to lofty blood-fat levels and depressed concentrations of high-density lipoprotein cholesterol (aka HDLC or ‘good cholesterol’).
Why is deep fat so hazardous? When fat cells inside your abdominal cavity release fat into the blood, the fat bobs straight to your liver, where it can be transformed quickly into VLDLs and LDLs – the ‘bad fats’ which are associated with an increased risk of coronary-artery disease. On the other hand, the fat that’s closeted inside your muscles and the fat released by fat cells located under your skin have a reasonable chance of being broken down by your muscles before they reach the liver.
Moderately paced, 50-90 minute workouts in nippy air are fantastic for breaking down fat, but slight adjustments in your workout schedule can force the fat-burning fires to kindle particularly fiercely. One strategy is to exercise for an hour in the evening about three hours after you have finished your dinner. Don’t eat after this workout, and then complete another 60-minute effort on the following morning before breakfast. Your muscles will be quite glycogen-depleted during the sunrise session, forcing fat to be metabolised at a higher than usual rate.
All of this sounds fine, but winter exercise is not all cake and icing. One of the problems with it is that we can simply get too cold. Oddly enough, the danger usually doesn’t originate in the frosty air per se but in the combination of frigid air and sweat. After all, cold air doesn’t shut down the sweating process, and we begin to lose heat at an accelerated rate as our clothing becomes saturated with moisture. Water is a terrible insulator (it conducts heat away from the body about 25 times faster than air), so sweat-soaked clothes can transform an initially comfortable workout into what feels like an arctic expedition. This can be especially dangerous if fatigue or injury produces a sudden downturn in exercise intensity. It’s a good idea to tie an extra-thick sweatshirt around your waist during all wintry excursions. You can put it on just in case the wind picks up or you become too tired to exercise vigorously.
Dealing with the ‘wind-chill’ effect
Always bear in mind that the actual coldness of a particular winter day depends not just on temperature but on wind speed, too. A moderately pleasant 41° F. temperature will suddenly feel like 32°F. if a nine mile-per-hour wind develops and the perceived coldness will plummet to about 23° F. with a 19-mph wind. It’s important to remember that movement can amplify or minimise this ‘wind chill’ effect. For example, running or cycling at 10 mph into a 9-mph wind provides the same chill as standing still in a 19-mph gale. For that reason, on windy days it’s important to complete the first half of all your winter workouts into the wind. The second half of the session – when fatigue is slowing you down, your body is generating less heat and your clothes are wet with sweat – should be completed with the wind at your back. Running at 8 mph with an 8-mph wind behind you totally eliminates any wind-chill effect, whereas running at the same speed into an 8-mph wind produces the chilling effects of a 16-mph squall.
Wintry exercise can be tough, but remember that it will do great things for you. After all, winter is a perfect time to carry out lots of endurance-building, fat-burning exercise. Your cold-weather training will eventually lead to some really sizzling efforts when warmer weather arrives.