Deciphering HIIT, Cardio, and Weightlifting
When it comes to weight loss, people often debate the relative merits of diet versus exercise: which results in greater–and more sustained–weight loss? While weight loss occurs during an energy deficit–that means you’re burning more calories than you’re taking in–study after study shows that creating that energy deficit is easier when you limit your caloric intake. It may take just five minutes to inhale a cinnamon roll, but it would take about 50 minutes of running to burn it off–and that wouldn’t even create an energy deficit!
Studies have also shown that most of us unknowingly compensate for the calories we burn off by eating more: in one study, participants who were asked to eat as many calories as they thought they had burned during exercise ended up eating three to four times as many calories as they actually burned. Further compounding this is the fact that exercise burns calories only to a certain extent: energy expenditure does increase with low to moderate amounts of exercise, but it tends to plateau at higher levels. That means that even if you were to try and burn off the burger and fries you just ate, you may not even be able to.
That being said, exercise does, of course, have benefits; it just shouldn’t be relied on as the only path to weight loss. In fact, multiple meta-analyses1,2 have shown that diet and exercise combined are more effective than either strategy alone for achieving long-term weight loss. In fact, 90% of members in the National Weight Control Registry–a research study that tracks individuals who have lost and kept off 30 pounds or more for longer than one year–exercise for at least 60 minutes per day. And, of course, exercise has benefits beyond weight loss: it can help reduce blood pressure and cholesterol levels as well as the risk of developing diabetes, cardiovascular disease, and osteoporosis; it can also increase muscle strength and flexibility, and improve sleep and mood.
Currently, the American Heart Association recommends getting at least 150 minutes per week of moderate activity or 75 minutes per week of vigorous activity. But what type of exercise should you be doing? Experts agree that, simply put, you should choose the type of exercise that you most enjoy doing so that you stick with it. Different types of exercise do have different benefits–from fat loss and muscle building to improved glucose tolerance (your cells’ ability to break down and process sugar) and a better cardiovascular profile–so mixing it up throughout the week is optimal in terms of health and weight loss.
Aerobic exercise, or cardio, is any type of exercise that gets your heart and breathing rate up. While your mind might first jump to running, biking, or swimming, it can also include activities like ice skating, sledding, or even mowing the lawn. Most of the calories burned from cardio happen during exercise as your body uses stored glycogen and fat as fuel sources. While calorie burn depends on a number of factors, including age, weight, and muscle mass, you can increase that number by increasing the intensity (going from level 4 to level 8 on the treadmill, for example).
Many of cardio’s benefits go far beyond the calorie burn. Just like any other muscle, your heart gets stronger when you exercise it, allowing it to pump more blood through the body per pump. In the long run, this leads to a healthier heart, a reduced risk of cardiovascular disease and stroke, increased circulation, and a reduction in blood pressure. It also improves the body’s ability to use glucose, thereby improving insulin sensitivity and reducing the risk of diabetes. Cardio can even benefit the brain: it’s been shown to reduce stress, improve mood, and even help manage conditions like depression and anxiety.
Even if you hate running, there are plenty of cardio exercise you can add to your routine. If you’re more of a creative type, try a dance fitness class like Zumba. Or if you thrive from competition, choose a spin class that shows your results on a screen in the front of the room.
HIIT stands for high intensity interval training. Unlike steady state cardio, which is done at a challenging but manageable pace for about twenty minutes or longer, HIIT is performed in smaller intervals (from about twenty seconds to a minute) at a higher intensity, with breaks in between. That might look like sprints (running, cycling, or swimming), shuttle runs, weighted circuits, or tabatas. One of the major appeals of HIIT is its relatively smaller time requirement compared to steady state cardio. Multiple studies have found that completing several small rounds of HIIT per week can result in improvements in VO2 max (a marker of aerobic fitness), skeletal muscle adaptations(positive changes in muscle structure and function), and improved insulin sensitivity (a measure of how quickly our cells respond to glucose; more insulin sensitivity means better blood sugar control).3,4,5
HIIT gets a lot of attention for its calorie burn due to something called the afterburn, or Excess Post-exercise Oxygen Consumption (EPOC). EPOC is the amount of oxygen required for your body to return to its normal resting state, which requires energy (that is, calories). A number of things must happen for your body to return to its resting state, including replenishing oxygen stores and ATP stores, removing lactic acid, and repairing muscle. All of these tasks require oxygen–and calories–meaning that you’ll continue to burn calories long after your workout is over. While the afterburn following HIIT is higher than it is for steady state cardio, it’s not super significant. For example, one study comparing the afterburn of low intensity exercise and high intensity exercise found that participants doing the high intensity routine burned 19 more calories in the three hours following exercise (41 calories versus 22).6,7 While these results are statistically significant, 19 additional calories is probably not enough to make much of a dent in your weight loss efforts.
High intensity interval training has its merits–it’s a great option for individuals who are easily bored with long bouts of cardio. It builds (and maintains) lean muscle and strengthens the cardiovascular system, and individuals who choose HIIT report a higher enjoyment of it over steady state cardio.
HIIT can be performed with any exercise, as long as you’re exercising at a high effort–about 90% of your VO2 max (that means an intensity at which your breathing is labored and you wouldn’t be able to chat with your exercise partner). If you’re a beginner, try it on a stationary bike (where it’s easier to keep time): sprint for 20 seconds and recover for about 40 or 60 seconds. Repeat that routine eight times. As you get stronger, faster, and more comfortable with HIIT, make the workout even harder by increasing the length of your high-intensity intervals and decreasing the length of your recovery periods.
You might not immediately think of weight lifting when you think of weight loss; after all, the goal of weight lifting is gaining muscle, right? But muscle is metabolically active–so the more you put on, the more calories you’ll burn at rest. Weightlifting contributes to a calorie deficit in three major ways: it burns calories while you do it; it elevates metabolism immediately following exercise as your body works hard to return to its resting state; and it promotes the formation of lean muscle mass, which burns more calories at rest. Adding weight lifting or resistance training to your routine has been shown to aid fat loss: one study found that dieters lost 14.6 pounds of fat in 12 weeks; dieters who also did aerobic exercise lost 15.6 pounds; and dieters who performed both aerobic exercise and weight lifting lost 21.1 pounds of fat.8
Beyond building muscle and burning calories, weight lifting improves bone health, which is especially important as you get older and bone mass decreases. Weight lifting has also been shown to improve cognitive abilities and self-esteem, reduce the risk of type 2 diabetes as well as cardiovascular disease, and limit chronic pain from arthritis and fibromyalgia.9 And, of course, when you’re stronger, everyday tasks become easier: think carrying groceries, lifting up kids, or shoveling the driveway.
If you’re new to weightlifting and have access to a personal trainer, it may be helpful to sign up for a few sessions so that you can learn proper form and develop a starting routine. If you don’t have access, see if your gym offers introductory weight training or resistance training classes. And if that’s also not an option, start with bodyweight exercises like squats, lunges, push-ups, and triceps dips. And don’t forget to take rest days: rest days are crucial for letting your muscles recover, as that’s when they get stronger.
Just like there is no ideal diet for everyone, there is no perfect or best workout for everyone. When it comes down to it, choose the exercise routine that you enjoy the most and that works with your personality and daily routines. And if you have some extra time or feel extra motivated, try a new class or add in some sprints or weights every now and then.