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Which One Will Help You Lose Weight More?

This is the eighth and final installment in our series on exercise.

And we have saved the biggest question for last.

What is more important when it comes to losing weight–exercise or diet?

According to surveys, most of us (70%) believe that diet and exercise have an equal impact on weight loss while 19% of us believe exercise is the most important factor. Only 11% believe diet is the most important.

As we will discover in this article, 89% of us are dead wrong.

Because studies clearly demonstrate that the essential factor in weight loss is what you eat…not how much you exercise.

Despite the fact that exercise brings us a myriad of powerful health benefits, weight loss is the one area where it falls short.

Let me explain why…

Fitness and Fat Are Both Climbing…

No doubt about it… physical activity is on the rise.

Our fitness-crazed cultures in the US and beyond see more and more of us lacing up our running/walking shoes or joining gyms and cross-training programs.

Despite the fact we are exercising more, we are still—steadily— gaining weight.

The statistics reveal a rather bleak picture.

Today over two-thirds of all Americans are overweight. Childhood obesity has tripled. And in just 14 short years away, experts predict that more than half of us will be clinically obese.  And the increased amount of calories consumed by Americans seems to be more than enough to explain the weight gained.

All that physical activity does not seem to be making us any thinner.

Why Exercise Cannot Stop Obesity…but Diet Can

Obesity—a condition that promotes chronic diseases and may shorten life expectancy— is nothing short of an epidemic.

Common wisdom blames our sedentary lifestyles for the obesity problem.

But our sitting around too much is just a tiny piece of the puzzle.

To tackle obesity, we need to focus on the real culprit, which is our diet and overconsumption of calories.

Just think about it. The average American eats the equivalent of a Big Mac in extra calories on a daily basis.  To work off the extra calories we would have to walk more than 2 hours a day, seven days a week.  If you have trouble squeezing 30 minutes of exercise three times a week into your busy schedule, try 130 minutes every single day!

Simply put, obesity has to be prevented or reversed by diet.

By what we put in our mouths.

Not how many hours we devote to the gym.

What the Studies Show

According to a 2011 meta-analysis, which looked at multiple studies on childhood obesity, being active is probably not the most important determinant in unhealthy weight gain in children. The same seems to hold true in the adult population.

Other studies suggest that exercise without dieting may actually cause weight gain.

For example, a recent study put 81 healthy but overweight women who had not exercised for a year on a new exercise regimen designed to improve cardiovascular health. Importantly, they were explicitly instructed not to change their eating habits for 12 weeks.

The results were startling.

  • 70% gained weight — some as much as 10 pounds.
  • The weight gained was from fat, not from added muscle.
  • A smaller percentage of participants did not lose any weight at all.

In sum, their cardiovascular fitness improved, but it did not lead to weight loss.

This is not to say that exercise does not play a role in weight loss. Exercise appears to contribute to long-term weight loss results—but only when used in combination with a healthful diet.

In a 1999 review of randomized trials, researchers reported a significant but overall small increase in weight loss when exercise was combined with diet while two more recent studies found that, in the long run, an exercise-diet combination led to slightly more weight loss versus diet alone. However, researchers also stated that “the evidence suggests a moderate superiority of diet over exercise” when it comes to measurements of body weight and fat mass alone.

Why Is Exercise Not Effective?

There are many reasons why exercise is less effective than diet when it comes to weight management.

  1. We Calculate Our Calorie Intake/Output Badly. All of us tend to overestimate the calories we burn through exercise and underestimate the amount we consume. According to a study published in the International Journal of Sports Medicine and Physical Fitness, normal weight individuals overestimated their calorie output by 3-4 folds!  And when asked to precisely compensate calories burned with food intake, the calories consumed were still 2-3 folds greater than the measured calorie output during exercise.
  2. Calorie Intake Is Fast and Easy While Calorie Output Is Slow and Hard. For exercise to make a difference, you need to do a lot of it. For example, you can easily eat two slices of a large cheese pizza (vegan or not) in under 3 minutes for a total of ~500 calories. Running on a treadmill at 10 mph (which is very hard to do) for the same amount of time will burn less than 40 calories.  In fact, a recent study on postmenopausal women calculated that a whopping total of 77 hours of exercise might be required to lose a single kilogram of fat! (That translates into ~35 hours of exercise for 1 pound of fat).
  3. Exercise Increases Appetite. For many, exercise increases appetite and leads to compensatory increased caloric intake, which often ‘cancels out’ the calories burned by the activity.
  4. Exercise May Decrease Daily Expenditure. Physical exhaustion produced by exercise may lead to less physical activity in everyday life for a surprising net loss in daily activity.
  5. Exercise May Give Us License to ‘Reward’ Ourselves. Exercise may sometimes lead to a common psychological trap. After working out, we feel justified in ‘rewarding’ ourselves by eating (especially the ‘bad stuff’). If we go overboard with our reward, we can easily erase or even reverse the good done by the exercise.

The Myth of Metabolism

Many mistakenly believe that physical activity ‘revs’ up your metabolism, which, in turn, will help you burn more calories. But if you examine the components of your metabolic rate, you will see there is a limit to how much effect exercise can really have.

To understand this, we need to review a few basic concepts.

The total amount of energy you burn on a daily basis is called Total Energy Expenditure or TEE. The biggest part of TEE comprises the Resting Metabolic Rate (RMR). This is the energy your body uses to stay alive. Even if you did not move an inch all day, you would still burn this amount. Your RMR will primarily depend on your weight and height, and the variation between any two equivalent individuals is quite small.

There is also the Thermic Effect of Food (TEF), which are the calories you burn to digest your food and absorb its nutrients, which is responsible for 10% of TEE.

Now let’s factor in NEAT (Non-Exercise Adaptive Thermogenesis). This is the energy you burn outside of RMR and is a reflection of how active you are in terms of ‘moving’ around through your day. While this is an area where people can impact their total energy burn, it also only accounts for 10% of TEE.

Lastly, the Thermic Effect of Activity (TEA) consists of the calories you burn during actual exercise. If you do the minimum recommended amount of exercise and walk for an hour 5 days a week, your TEA will represent another 10% of your total daily calorie burn.

It is evident that calorie expenditure in terms of exercise is not that big in the grand scheme of things. But there’s more to know about your metabolism…

The bitter truth is that the more you lose weight, the more your RMR decreases (i.e. a smaller body requires less energy to survive). And contrary to popular belief, exercise cannot counter or reverse this.

All of this brings us back to the same message. The real culprit when it comes to weight gain is an overconsumption of calories, not too little exercise. As described in a review article aimed to clear the confusion about the leverage of exercise on body weight, ‘the energy balance (i.e. calorie in versus calorie out) equation suggests that energy intake and energy expenditure occupy equivalent roles in determining energy balance, when in fact the factors governing energy intakes influence the energy balance far more powerfully than the factors determining resting energy expenditure’. (Bolded mine)

Eat Your Way to a Healthy Weight

So, if you are looking to lose weight or control it, you need to pay attention to what you are eating!

This does not mean that you have to starve yourself.

The best route to go is to eat a wide variety of whole plant foods that are naturally low in calories.

This is because—by definition—a whole food plant-based diet is a low energy density diet—satisfying and satiating without piling on the excess calories.

So eat—not exercise—your way to a healthy weight.

One of the best pieces of advice I have ever heard is that 5 to 10 minutes a day with a food diary is more valuable than 30 minutes in the gym.

And remember that you do not need to do everything right all of the time.

My motto about weight loss?

Embrace consistency and imperfection.

It is okay to not be ‘perfect’ all the time. But be consistent.

And keep taking baby steps. You will see the results.

Rosane Oliveira, DVM, PhD

President & CEO, Plant-Based Life Foundation | Dr. Rosane Oliveira combines a lifelong passion for nutrition with 25 years of genetics research to create programs that help people develop healthy habits on their journey towards a more plant-based lifestyle. She is a Visiting Clinical Professor in Public Health Sciences and was the founding director of the first Integrative Medicine program at the UC Davis School of Medicine. She completed her postgraduate studies in Brazil and did her postdoctoral training in immunogenetics and functional genomics at the University of Illinois at Urbana-Champaign.