There are two major wings of the fitness industry. One (the more popular one) tells people to hop onto a treadmill for long periods of time or go out for a long jog if you want to lose fat. Go to any commercial gym in the country and I bet you'll find long rows of treadmills, bikes, and elliptical riders with chubby people slogging away for 30+ minutes at a time trying to "burn off" the holiday cheesecake they ate the night before. Another wing tells you to never, ever do long slow distance training (LSD), but to instead train using only high intensity intervals of some kind - sprints, Tabatas, barbell complexes, crossfit; some version of high intensity metabolic conditioning.
Neither approach is entirely wrong or entirely right. You can see the problems with LSD pretty easily - just go to the gym and see how fast the bodies change on the people using the cardio machines. They're often the same month after month, and in some instances get worse-looking. Chronic long-duration cardio increases cortisol levels, breaks down muscle, increases fat retention, and has a whole host of health consequences. The high intensity side is less troubling, but it can easily be overdone. Too much metabolic conditioning can easily lead to overtraining and injury, and it's hard to get your workouts in when you're hurt.
What's the right way? They're both righ. Sort of. Here's the key: the interventions you need to make to lose fat in a healthy way have to be done in a specific order - there's a hierarchy of fat loss methods. I don't just mean that the top methods are better - I mean that if you take any methods from the middle of the list or skip any, you might see some results for a little while but they won't be nearly as good as if you go in order. In other words, step 1 is necessary for fat loss; doing steps 1 and 2 is better yet, but step 2 alone just won't work. Same idea as we go on down the list - doing any steps while skipping the ones before it will seriously compromise your results. Now to the list (remember, it's a numbered list because the order is important!):
1. Reduce your food intake. This may seem like a no-brainer, but if you're fat you have to reduce your food intake to lose weight. Now there are some outlying exceptions to this - sometimes people who diet for long periods of time need to do a re-feed to get their metabolism working properly, but in almost all cases you're fat because you've been eating too much.
This isn't as simple as cutting calories, but it's close. Calories are a bad measure of food/ energy intake for a few reasons - fiber is counted wrong, absorption isn't taken into account, etc. If you're eating the same types of foods then you have to cut calories. If you're radically changing the composition of your diet then things get more complicated but the bottom line doesn't change - reduce intake.
What about food quality? Food quality is important for health and for compliance reasons - it's much easier to stick to a low calorie, high quality diet (meat, fat, veggies) than a low calorie, low quality diet (Twinkies). It's also healtheir. But it's not actually necessary for short term fat loss - that nutrition professor who lost weight on the Twinkie diet showed that (not recommended for long term weight management). I strongly advocate eating better but more than that you have to eat less if your goal is fat loss.
What about just exercising more? Well, this typically doesn't work. Most people will just eat a little more - they'll be hungrier - if their activity level increases. It's much easier to eat an extra few hundred calories than to "work off" a few hundred in the gym. If you can manage to exactly control how much you eat - weighing and measuring your food - then you might lose weight without actually redudcing food intake, but it's going to feel exactly like a diet. If you free-feed (as in, eat what you want without weighing and measuring and stopping yourself at pre-determined points) you're going to eat more food the more work you do and you won't lose fat, or not much fat (again, there are outliers who can get away with this, just like there are people who smoke and drink and live to be 100, but do you want to count on being one of them?)
2. Strength train. Why? Simple - if you follow #1 you're going to burn body mass. If you strength train you have a fighting chance of keeping whatever muscle you already have. If you don't then your body is too likely to burn muscle for energy instead of fat, which is bad for a whole bunch of reasons.
First, muscle burns calories, so losing muscle lowers your energy requirements and forces you to keep reducing your food intake in a bad spiral into weakness and feeling crappy. Muscle also looks good - almost nobody has "too much muscle" from an aesthetic perspective (those who think they do are usually just fat) unless they're high level competitive bodybuilders or strength athletes who are taking enough exogenous androgens to put 5 teenagers through puberty. Muscle is also the only thing standing between you and decrepitude - go into any nursing home and find someone confined to a wheelchair with big, muscular legs (there's a cause and effect issue here, but studies have shown that when elderly people do strength training and gain leg muscle they often throw away their canes and walkers).
Your strength training should take 20-30 minutes (after warmup) and be done 2-3 times per week.
3. Do some High Intensity Intervals. Sprints, Tabatas, kettlebell sets, burpees, whatever. There are two reasons for this: First, HIIT will stimulate your metabolism and hel you burn calories - you might work out for 10 minutes but get an afterburn effect where your body burns extra calories for the next 36 hours. Second, you need to raise the ceiling of your cardiovascular capacity for health reasons. You want your heart and lungs capable of supporting bursts of really hard work without exploding so you can survive to enjoy your fat loss. Seriously - when do people get heart attacks? It's not usually from watching tv for hours on end - they die when they do something relatively strenuous (remember, taking a crap can be strenuous if you're sedentary enough). The better adapted you are to really, really hard efforts the less likely you are to die doing one.
The other side of the high intensity coin is that more is not always better. HIIT is a serious stress on the body - doing too much of it can raise cortisol and mess up your health just as much as doing too much LSD. So keep the sessions brief, intense, and relatively infrequent.
Your HIIT sessions should be done 1-3 times per week for 5-15 minutes at a time.
4. Slow Low Intensity Distance Exercise (SLIDE). Now we get to the title of this post! Okay, SLIDE type exercise - think a long walk, a casual bike ride across town, even walking on a treadmill while reading or watching TV - has gotten a bad rap. On it's own it won't help you lose fat. It won't get you in shape. It won't improve bone density. It won't build muscle. If you do it with a little too much intensity - if you go from a walk to a slow jog - it will tear down muscle, increase cortisol, and wear down your joints and immune system. All in all, bad!
But SLIDE can serve some important functions in a fat loss program if it's done right. First of all note the number - this is intervention #4! SLIDE can improve your fat loss program but ONLY if you are already doing steps 1-3. SLIDE alone is useless for fat loss. Second, your SLIDE must be low intensity! Your hourlong evening walk is great for fat loss but if you turn it into a power walk where you're huffing and puffing and swinging dumbells while you do it for an extra burn you're going to make it harder to lose weight, not easier (because you'll be dumping cortisol into your system).
What are the benefits of SLIDE? First, you'll burn extra calories, and mostly fat calories. If you want to burn even more fat do it right after a higher intensity session - the high intensity work dumps fatty acids into your blood, the SLIDE will use them up. That's not necessary, though - SLIDE done first thing in the morning or at night will work fine for burning up extra fat. Not enough to overcome a bad diet or lack of strength training - but remember, we're already making sure we do steps 1-3, so that's not a problem!
SLIDE also has psychological and health benefits. Most people feel good when then move a lot. We're not adapted to spending all day sitting in an office, and our bodies perform better under a lot of low level stimulation. This is a way to tell if you're going too hard - if your SLIDE sessions make you tired and wiped out your intensity is too high. You should end your nice walk feeling energized and alive, not drained and ready for a shower. You can double the benefits by talking a walk with someone. There's a ton of research showing significant health benefits to having social interactions with other people, and I promise your marriage will improve if you take a long walk with your significant other every day (or, if your marriage sucks, it will deteriorate rapidly so you can get it over with and try again with somebody else).
Walks (with or without dogs), casual bike rides, throwing a frisbee around - any low intensity long duration activity can work as SLIDE. You'll feel better, lose fat a bit quicker, and be happier. Just remember the keys:
- Prioritize steps 1-3 - if you're not doing those then SLIDE will be nice but won't get you lean.
- Keep your intensity for your HIIT sessions - don't let your SLIDE "workouts" turn into real workouts.
- Incorporate more low intensity movement into your day wherever possible. Fidget, park farther from work, take stairs instead of an elevator - none of these things will replace eating less, strength training, or high intensity cardio, but they will add benefits if you already do those other things.