Weight loss is a science. It's a complicated and imperfect one, but it's still a science, which is why it's best to follow what research says if you want to successfully achieve your goals. Most research can't definitively say for sure that, "Yes, this is the exact answer." But it can tell us what is likely true and help to point us in the right direction. Here's what recent science has to say about some of the most commonly misunderstood ideas about weight loss.
"Stop wasting time doing exercise in a 'fat-burning zone,'"says Shawn M. Talbott, Ph.D., a nutritional biochemist and the author of over 200 articles and 10 books on nutrition, fitness, and wellness. "This tends to be lower intensity exercise with the intention of optimizing fat metabolism, but it is actually a waste of time because you could be burning twice the number of calories in the same amount of time or the same number of calories in half the time with a regimen of higher-intensity interval training." One study from 2002 found that cyclists burned fat at the highest rate when exercising at a level equivalent to 74 percent of their maximum heart rate and another from 2004 that compared 30 minutes of running and cycling at three different intensities (55, 65, and 75 percent of VO2 max) found that the highest rate of fat burn occurred at 75 percent VO2 max.
"Research shows drinking diet soda is more likely to cause weight gain than non diet soda and may lead to health problems including diabetes and heart disease," says Holly Stokes, a certified Hypnotherapist and Neuro-Linguistic Programming (NLP) Practitioner and author of A Lighter You! Train Your Brain to Slim Your Body. According to WebMD, eight years of data collected by researchers at the University of Texas Health Science Center in San Antonio found that a person's risk for being overweight increased by 41 percent for every can or bottle of diet soft drink consumed each day.
According to Paul Kriegler, corporate registered dietitian at Life Time Fitness, there's not a strong amount of evidence that suggests saturated fats or cholesterol can be linked to rising obesity rates and weight gain. One study conducted by the Annals of Internal Medicine found that subjects who followed a calorie-controlled low-carb diet that allowed for unlimited amounts of protein and fat, lost the same amount of weight as subjects who followed a diet that limited fat intake to 30 percent of their total calories each day. However, the results found that the lower-carb, higher-fat diet did yield better health outcomes like improved blood lipid profiles, blood pressure, and waist circumference.
While the study that Kriegler mentioned did find that a diet consisting of less simple carbohydrates (like from white rice, white bread, and candy) was associated with better health outcomes, the idea that carbs can make you gain weight is not true. “Your body needs a certain amount of carbs, fat and protein to function,” says Lauren Brown a trainer and sports nutritionist for Balanced Fitness and Health. “Carbohydrates are the body’s number one go-to for fuel. Without it you will eventually lack energy, experience brain fog, and feel depressed and moody." For weight loss and overall better health, she suggests choosing carbohydrates that come from nutritious sources like vegetables, fruits and whole grains.
"You cannot 'spot-reduce' and 'tell' your body where to get rid of fat stores by doing exercises that target that region," says Bowflex Fitness Advisor, Tom Holland. In order to reduce fat in any area of your body, you have to reduce your overall body fat percentage with a combination of exercise, healthy eating, quality sleep habits, and stress reduction. While there is a small amount of research that says you may actually be able to "choose where you loose," for the most part, science has shown that targeted exercises are not the best way to burn fat around a specific area of the body.
OK, so the science behind this training strategy is a little bit complicated. According to Holland, most research shows that fat burn is consistent whether you eat before or after a workout. However, according to BodyBuilding.com, one study published in the British Journal of Nutrition found that participants burned 20 percent more calories from fat when they didn't eat before performing a morning cardio workout. But as Jim Stoppani, Ph.D. reports, "The story doesn't end here, however. Your body also breaks down amino acids into glucose overnight, so fasted morning cardio mobilizes more fat and potentially more amino acids for fuel, which isn't ideal if building muscle is your primary goal." The bottom line: your nutritional strategy should depend on your goals. "If you're like most people, your best bet is to not worry about doing cardio fasted first thing in the morning," Stoppani wrote. The better bet, as Talbott mentioned earlier, is performing high-intensity interval workouts, which studies have shown can help you to burn more calories and fat throughout the day and will ultimately lead to greater fat loss over time.
On paper, this widely popular concept might seem true. However, it fails to account for the way the body processes food, which varies greatly from one individual to the next. In fact, one recent study that overfed 16 male and female subjects by 1,000 calories for eight weeks (which, according to the one pound=3,500 calorie idea, should have led each subject to gain 16 pounds) resulted in entirely different weight gain amounts for each of the participants. Obesity expert Dr. Yoni Freedhoff summed the idea up nicely in an article on Greatist saying, “People have different fuel efficiencies, whereby two people eating the same number of calories may see markedly different impacts of those calories upon their weights.”
Exercising and eating right are important for weight loss, but a growing body of research shows that healthy sleeping habits may be equally as important. A recent study published in the journal Sleep found that people who get adequate amounts of sleep on a regular basis may have a lower risk for weight gain compared to those who are sleep-deprived.
According to Rachele Pojednic, Ph.D., a nutrition researcher at Harvard Medical School, unless you suffer from celiac disease, there's not much scientific support to back the claim that eating gluten-free is healthier or a smart strategy for weight loss. “Cutting gluten out of your diet most often leads to a reduction in overall calories, simply due to the sheer amount of grain based foods that we eat on a regular basis,” Pojednic said. “Pasta, bagels, bread, and crackers are typically cut from the diet and, early on, are not replaced when people go gluten free. This can lead to noticeable reductions in weight at first. However, over time, most people find ways to reintroduce these calories into their diet by way of 'gluten-free' products.”
While high-intensity cardio is likely one of the most effective strategies for reducing overall body fat, it's really only one part of the big exercise picture. A recent study from the Harvard T.H. Chan School of Public Health highlights the importance of including both cardio and resistance training in your workout routine. The study focused on belly fat reduction specifically and found that when compared with men who increased time spent on different types of aerobic exercise (including yard work and stair climbing), the men who increased the time they spent training with weights by a similar amount (about 20 minutes a day) gained less weight in their waist.