Is Too Much HIIT Hurting Your Fat Loss Efforts?
Just because HIIT is trendy doesn't mean longer duration cardio (aka L.I.S.S) suddenly became pointless. I frequently get comments from prospective clients along the lines of "not wanting to do tons of cardio." And while it's very true that too much cardio while dieting can have a negative impact on the metabolism , that doesn't mean ALL cardio is counterproductive. The right amount of cardio, and the right TYPE can be incredibly beneficial in weight management and fat loss. I know HIIT is the trend, but trust me when I say L.I.S.S is still highly relevant.
Longer duration cardio sessions performed at lower intensity levels have positive impact for almost anyone regardless of their fitness goals, but are particularly effective when fat loss is a focus.
1) L.I.S.S is restorative. One way in which I like to implement it in the programs of my clients is to follow up a day of hard strength training by prescribing a 40-50 minute low intensity walk. It helps to alleviate muscle soreness from weight training, helps flush toxins and reduces lactic acid buildup. It also helps strengthen joints and ligaments and provides scientifically backed mental and physical stress relief by helping to lower cortisol levels and balance the hormones.
2) A healthy aerobic system is a key component of health regardless of your goals. It lowers resting heart rate, boosts capillary density and oxygen transport, elevates lung diffusion capacity, and maximizes lung ventilation. What does all this mean? It means that when you have a strong aerobic capability you improve the efficiency with which the entire body works. Cardio health even impacts how efficiently your body transports and metabolizes nutrients, which has a direct impact on other body composition or strength goals.
3) Low intensity work burns fat. Yes, HIIT does too, but mostly through the afterburn effect. Low intensity cardio burns fat during the actual training. Typically the body relies on carbs for fuel when it comes to short bursts of activity, but after about 12 minutes of consistent activity the body shifts from using carbs to using fat for fuel. The percentage at which your body uses fat versus carbs for fuel increases as the workout continues. It's estimated that about 35% of energy utilized during HIIT is fat, the remainder is carbs while 50% or more of the energy used during L.I.S.S comes from fat.
4) Low intensity cardio helps preserve muscle, particularly when in a caloric deficit. It's a hormonal thing. Moderate intensity cardio – the type that most people think they need to do for fat loss - will increase cortisol levels beyond what's optimal. The activity is intense enough to stimulate the release of cortisol, and long enough to elevate it significantly, and since cortisol is catabolic, this can put you at risk of losing hard earned muscle. Low-intensity cardio, on the other hand, like a 40-60 minute walk is not intense enough to stimulate much cortisol release and can actually lower cortisol levels by having a relaxing effect.
5) Lower intensity cardio also helps with appetite control, which is another reason I like it when dieting. Again, it comes down to hormones. Research from the January 2009 "American Journal of Physiology: Regulatory, Integrative and Comparative Physiology" indicates that long sessions of low intensity cardio can influence hormone activity in a manner that blunts hunger. A study found that a 60-minute session of cardio (walking), done at a very low intensity, increased the body's release of leptin (appetite-blunting hormone) and decreased the release of ghrelin (hormone that promotes hunger) and cortisol, which also had an appetite increasing effect. HIIT on the other hand can stimulate the appetite. High-intensity workouts, particularly ones that are longer in duration (10:00 or longer) place more stress on the body and cortisol, the hormone released in response she to stress can stimulate the appetite. During HITT the body temperature increases more, anabolic and stress hormones are produced, your heart and lungs have to work harder, fuel stores get spent and more lactate builds up in your bloodstream. During the recovery period, your body has to expend more energy to restore homeostasis and this can also cause an increase in hunger.
Typically, when dieting or trying to lose weight I like to see most cardio either be high intensity and super short in duration (maybe 2 sessions a week) or very low in intensity and long in duration (3-4 sessions a week).
My favorite ways to do L.I.S.S? I like long morning walks, adding a weighted vest, pulling a light sled, walking my dogs, doing long low intensity stepmill sessions, or low intensity incline treadmill walking.