Diet versus exercise: what is more effective for weight loss and health?

Many people think that it is possible to effectively manage body weight with low calorie diet only and absolutely no exercise or little physical activity. They believe that by simply switching from coke to diet coke or from red meat to chicken breast or eating some kind of “omega-3” supplement they can lose weight and be healthy. This is one of the most common myths about weight loss. The market is full of products that help you “burn fat”.

Sugar-blocking brownies… Wow!
Very often, attempts to shed pounds with diet only either fail miserably or weight is quickly regained after diet regime is stopped. Here is why: with low calorie diet only, you will lose both fat and muscle. Because muscle burns most calories in your body, dieting only will cause a decrease in your energy producing capacity, or metabolic rate, and therefore a decrease in your endurance, fitness and strength. When you start cutting down your calorie intake, the first thing your body does is shutting down energy usage in order to save energy. Stop your diet for a while and quickly regain all those pounds lost and even put some extra!

Muscles are you body’s power machines – they burn food you eat into energy. It is the physical activity and exercise that maintains oxygen supply and energy production ability of your muscles in top shape. No exercise = slow loss of muscle = burn less food into energy = gain weight = become less fit. This process will be happening naturally as you age, no matter what you eat. This weight gain is not merely an increase in fat tissue – it is more a conversion of muscle mass into fat mass.

The best results for both weight loss and maintaining your metabolic rate are achieved when low calorie diet and exercise regime are combined together, which is shown on the diagram below.

Exercise only regime (bottom right) is still a better choice than going low calorie diet only. Exercise only will not necessarily result in a net weight loss, but if done correctly, it will result in losing fat mass while building up muscle. This alone will make you a whole lot fitter, even with no net weight change. When you are exercising, even minor adjustments to your diet, such as just cutting down on soft drinks, will have noticeable effect – because now you body is more limited for energy. Your muscles have a lot more blood flowing through them and burn a lot more calories, during exercise and after exercise, and even when you sleep. Reduce energy supply by a little – and observe a significant weight loss.

Every form of physical activity counts – light activity (standing and walking), moderate activity (brisk walking, bicycling), aerobic exercise and resistance exercise. Whether you can put in an extra 10 minutes of jogging, do an extra set of yoga, park at the far corner of a parking lot to have a little walk, or stand at your office job – do it. They all work through somewhat different mechanisms, but they all are good for you. Just like there is no “magic” organic food, there is also no single “magic” exercise. All forms of physical activity are great, but the best ones are the ones you enjoy!

If you do not maintain a necessary level of physical activity as you age and, your metabolic rate will gradually decrease. At the same time, as you advance in your career, your job usually becomes more sedentary. (Few people still flip burgers in their forties). That is why most people, as they progress from their 20s to their 50s, gain weight. This slow weight gain is detrimental to health. In one study reference below, individuals with high weight gain (22 lbs) between ages 20 to 50 years had 4-5 times higher risk of chronic disease (cardiovascular and diabetes) than folks who did not gain weight (from Haffner,2006):

Some people may say that this reasoning is wrong, because they know a lot of people who do not exercise and are lean in their 40s, 50s, and 60s. This is true, because your energy balance and weight also depends on your genetic makeup. I have two objections to this. First, this is a minority of people – most people do gain weight as adults. It is a fact. Just think of your last college reunion. Did many people look as fit as they did in their 20s? Second, even though these people are lean it does not mean that they are also healthy. They are fitter that overweight folks, but nowhere nearly as fit as the lean folks who also exercise. I had a lean friend of mine who thought he was healthy. He even played tennis sometimes. He died from a heart attack, at age 52.

Scientists can never figure out exactly what diet is right. Few years ago, they were recommending reducing fats. Then cooking oil became the culprit. Then there was talk about virtues of fish oil, flax seed oil, vitamin pills, and so on. We are always looking for an easy in-the-bottle solution, which requires no effort on our side. There is still “fat versus carbohydrate” argument going on right now, with neither side winning. Most of these recommendations later did not confirm, and even when effects were significant, they were relatively small (which is one reason why they are hard to prove). The only food that is consistently proven to be very unhealthy is simple (sweet) sugars, because they tend to mess up your blood lipid and glucose profile.

The level of physical activity and fitness are by far stronger predictors of mortality and risk of chronic disease (cardiovascular, diabetes) than the exact composition of food you eat. In various studies, effects of physical activity and fitness level on reducing risk of cardiovascular disease and all cause death were measured into 2 to 3 fold. And there is no disagreement on this in the scientific community; only research on mechanisms of how physical activity improves various functions of human body.

So, if you were thinking that you could significantly improve your health by somehow mixing just the perfect amount of protein, fiber, omega-3 fatty acids, and vitamin pills, while still comfortably sitting in your chair most of the time, keep dreaming. When we were apes and prehistoric humans, we were not spending days cooking and mixing perfect food – we were spending most of our time trying to find, catch or kill it. And our body was happy with whatever we could obtain.

Do not get my message wrong though. I have a whole chapter on nutrition here. Nutrition is very important and can prime your body to flourish, but good nutrition alone does surprisingly little. Combine it with some exercise – and see your body respond immediately and robustly!

The importance of diet is overstressed, while physical activity and sleep regime in underestimated. The reason for this is simple – foods are easy to advertise and sell and require no effort on your sideother than spending some extra bucks. And most people want something with no effort. That is why the market is flooded with all kind of nutrition and food supplement products.

Some of those products are certainly good. Free-ranging eggs and vegetables from Whole Foods are definitely higher quality and better choices than same products from cheap Mexican stores. But they do no magic. Exercise and physical activity requires significant effort on your side and it is harder to sell to you. If you noticed, most exercise products on the market aim to decrease your time and effort invested in exercise, such as “get flat abs in 10 minutes a day” or “get perfect abs with no crunches”” and so on.

These strategies might work for some people who are lucky to have a perfect genetic makeup. They are primed to burn energy and have a significant response even to a small amount of exercise.

For the vast majority of us magic will not happen. So instead of trying to decrease your exercise time, come up with clever and creative strategies to increase it and integrate physical activity in your daily routine whenever possible. Not just vigorous exercise, but also light and moderate physical activity, such as simply standing and walking instead of sitting. When I started in 2012, my personal goal was about 30 minutes of aerobic and 30 minutes of resistance exercise on most days as well as doing my regular activities at work and at home while standing and walking.

So the bottom line is:

Whether or not you want to go on a low calorie diet, do exercise.

Recent research study says that those who exercise even tend to earn more money. When you are physically fit, you will perceive yourself differently, and the world will perceive you differently. Whether you are trying to lose weight, maintain normal weight, increase strength and endurance, reduce risk of most diseases, extend your life or do it all at the same time – do exercise!


Relationship of metabolic risk factors and development of cardiovascular disease and diabetes.
Haffner SM. Obesity (Silver Spring). 2006 Jun;14 Suppl 3:121S-127S.

Physical activity, fitness and fatness: relations to mortality, morbidity and disease risk factors. A systematic review.
Fogelholm M. Obes Rev. 2010 Mar;11(3):202-21.

Cardiorespiratory fitness, body composition, and all-cause and cardiovascular disease mortality in men.
Lee CD, Blair SN, Jackson AS. Am J Clin Nutr. 1999 Mar;69(3):373-80.

Relationship between low cardiorespiratory fitness and mortality in normal-weight, overweight, and obese men.
Wei M and others. JAMA. 1999 Oct 27;282(16):1547-53.

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