I've spent most of my professional practice as a dietitian working with clients on weight management, and one of the questions that pops up frequently is, "Which matters most for weight loss - diet or exercise?" People want to prioritize their efforts, so I understand why they'd ask the question. Most studies, as well as my experience, provide evidence that dietary changes alone produce greater weight loss results than exercise alone. For some people this makes complete sense while others are interestingly surprised. I find that some people believe that exercise will make more of the difference, so they will focus their efforts on that. However, without making changes in their diet, most people will struggle to lose a significant amount of weight through exercise alone.
Here's why. There are approximately 3500 calories in a pound of fat. So to lose one pound of fat per week, one would need to create a caloric deficit of 500 calories per day. Let's use an example of a person who weighs 150 pounds. If this individual wanted to focus on exercise to lose one pound per week, that person would need to burn at least an extra 500 calories per day above and beyond what she's currently doing. This is the equivalent of running 5 miles per day or walking on the stair climbing machine for 50 minutes per day or bicycling for 56 minutes per day or swimming for 1 hour per day. I'm not saying this is impossible, but it could be tough for someone to make that type of change. How do I know? I've seen it happen quite a bit. I'll get a client who's been working out like mad with a trainer with minimal weight loss results and lots of frustration.
On the other hand, if this individual wanted to focus on dietary modifications to lose one pound per week, that person would need to create a caloric deficit in the diet of about 500 calories per day. While there are many ways to do this, here's one example of how this could work. Maybe instead of a tall vanilla latte-no whip for breakfast, she switches to a tall nonfat latte for a savings of 160 calories. Instead of putting 2 Tbsp of peanut butter on her whole wheat English muffin, she opts for 1 Tbsp and saves 100 calories. Instead of 2 ounces of almonds for a morning snack, she opts for 1 ounce and saves 170 calories. Instead of 1 Tbsp mayonnaise on the turkey sandwich at lunch, she opts for 2 Tbsp of avocado and saves 50 calories. Instead of 1 cup of brown rice for dinner, she opts for 1/2 cup of brown rice and 1/2 cup of a California vegetable medley and saves 50 calories. These modest dietary changes alone created a caloric deficit of 530 calories over the course of the day.
At the end of the day, though, I tell my clients this...a combination of both dietary changes and physical activity is the best strategy for long-term weight management. Burning an average of 250 calories a day through exercise and making some small changes in the diet to save another 250 calories is likely a lot more manageable for someone to do. While more exercise is ideal, this is a great place to start or at least build up to in the beginning. In addition, there are many benefits to becoming more physically active other than weight loss -- reducing the risk for chronic diseases such as heart disease, type 2 diabetes, and cancer, strengthening muscles and bones, improving mental health and well being, better sleep, and more! In fact, exercise is so vital to health that doctors are now being encouraged to prescribe exercise, like they would medicine, to their patients. One other side effect of including physical activity in a weight loss plan is that people tend to eat better when they are being physically active on a regular basis. I often find that when physical activity goes to the wayside, so does the diet. In fact, research studies have shown that people who incorporate regular physical activity into their routine tend to better manage their weight long-term.
My honest opinion is that we do not have an epidemic of overweight and obesity in our country, but rather we have an epidemic of poor nutrition and inadequate physical activity. These are the primary causes of a variety health-related problems for many people, and overweight and obesity are really just a couple of the possible symptoms of those underlying problems. Rather than focus so much energy trying to see a certain number on the scale, I encourage my clients to focus on the behaviors of eating more nutritious foods and incorporating more physical activity into their lives. The weight, along with many other health benefits, will follow. And that, my friends, is my two cents:)
What do you think?