Why diet matters more than exercise when you're trying to lose weight

Weight loss is all about the number of calories you consume.

An estimated 160 million Americans are obese or overweight, according to an analysis published in the scientific journal The Lancet in 2014. The proportion of individuals with a body mass index of over 25 kg/m2 has risen sharply (29%) between 1980 and 2013.


“Being overweight or even obese is a growing, unchecked problem in the US today,” said Dr. Ali Mokdad, Professor of Global Health at IHME and a co-author of the study. “We are looking at a major public health epidemic that must be stopped.”


The most popular intervention strategies to combat obesity include making lifestyle changes to diet and adopting an exercise regime. But when it comes to dropping the pounds, what’s more important – diet or exercise?


The unit of food

Before we get to the bottom of the diet versus exercise debate, let’s examine the unit of energy from food – the calorie. The foods you eat store energy which the human body uses to power its cellular processes. The unit of this energy is the calorie. Different foods contain different amounts of calories per gram. Joghurt, for example, has around 60 calories per 100 grams whilst chocolate has 546 calories per 100 grams. That’s because the macronutrients (fats, proteins, and carbohydrates) that make up our food vary when it comes to energy content. Whilst fat has 9 calories per gram, proteins and carbs have an average of 4 calories per gram. Because chocolate contains more fat than joghurt, it makes sense that it has a higher calorie count.


How the body burns calories

Our body needs to burn energy to work. Every time you move a muscle or blink, energy stored by the body is used to perform that physical action. But there are many activities executed ‘silently’ by our major organs such as the liver, the brain and the heart. We just can’t feel them. 


Around 10% of the energy from food is used to power digestive processes and roughly 20% is used for physical processes and exercise. That leaves a whopping 70% of calories being burned to maintain body temperature and other organ functions.


Average calorie consumption per day

We need energy to live. But how much? According to recommendations, women should consume around 2,000 calories per day and men around 2,500 calories. Cutting just 500 calories daily could help men and women lose around one pound per week. But weight loss is a tricky business and varies by age, body height, and individual metabolism. If you exercise regularly, you can shift even more pounds. But unfortunately, exercise alone will not help you lose weight.


How to lose weight

Weight loss is about how many calories you consume. There’s just no way around it. If you need to lose a few pounds, you shouldn’t expect to shift any weight by stepping on a treadmill once a week if you continue to eat as usual. That’s not to say exercise isn’t an important part of a weight-loss regime, but a review by scientists at East Carolina University in the U.S. found that moderate exercise resulted in small weight loss. Only intensive physical activity did have a bigger effect on overall weight.


Eat smart instead. One way to consume fewer calories is to eat smaller portions. There are tons of studies which have shown that portion size makes a big difference to the overall calories people consume. We’ve all been taught to finish the food on our plates as children and it’s difficult to break these habits when we’re adults. But one way to trick ourselves into eating less is simply to minimize the portion in front of us. Studies have shown that people who dieted smart without exercising lost 23 pounds in 15 weeks, whilst those who only exercised lost just 6 pounds in 21 weeks.


One great way to keep check of the calories you consume is to use an app like MyFitnessPall, Fooducate or Lifesum. These allow you to enter the foods you eat and monitor the number of calories you consume. Many apps also let you add the exercise you performed in a day. By monitoring your diet, you may be more aware of your total caloric intake and make better choices in the future. But don’t become obsessed with tracking what you eat because excessive thinking about food can quickly lead to an eating disorder. Maintain a healthy balance to your body and allow yourself a treat once in a while.


If apps aren’t your thing, you could try meal replacement plans. There are lots on the market - from shakes to meal packages delivered right to your door. The idea is that by sticking to the recommended portions, you consume fewer calories in a day and lose weight over time. Studies have shown that meal replacement shakes are an effective way to shed excess weight.


Cut the bad stuff and make the good stuff tasty. Weight loss isn’t a race to reach a number on a scale. It’s about gradually reducing belly size by modifying your lifestyle. That’s not to say you can’t ever eat French fries again, but it’s important to realize that hyper-palatable foods (those that we usually find delicious) are often bad for overall health. It’s true: trans fats often used to cook fries aren’t just bad for your waist, but also bad for your heart and brain. If you find the thought of eating raw veggies unbearable, fear not. There are plenty of great recipes to help you cook delicious but nutritious meals.


Most importantly, be patient. Weight loss takes time. Combine a few of the dietary strategies above for the best results. Don’t forget to exercise because physical activity is great for cell turnover and for boosting heart health.



  1. The vast majority of American adults are overweight or obese, and weight is a growing problem among US children. (2018, November 27). Retrieved from Institute for Health Metrics and Evaluation website: http://www.healthdata.org/news-release/vast-majority-american-adults-are-overweight-or-obese-and-weight-growing-problem-among
  2. Three Ways the Body Uses Energy. (2018). Retrieved October 16, 2019, from Sciencing website: https://sciencing.com/three-ways-body-uses-energy-8706999.html
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  4. Benton D. (2015). Portion size: what we know and what we need to know. Critical reviews in food science and nutrition, 55(7), 988–1004. https://doi.org/10.1080/10408398.2012.679980
  5. Yolanda Lewis-Ragland Md. (2018). DR. YOLANDA’S S.O.U.L. FOOD THERAPY?: how savory, organic, unprocessed, living food saves lives. S.L.: Balboa Press.
  6. Spratt, V. (2019, July 8). The Sinister Side Of Fasting & Fitness Apps That No One’s Talking About. Retrieved October 16, 2019, from Refinery29.com website: https://www.refinery29.com/en-gb/2019/07/235423/meal-tracking-apps-eating-disorder
  7. Davis, L. M., Coleman, C., Kiel, J., Rampolla, J., Hutchisen, T., Ford, L., … Hanlon-Mitola, A. (2010). Efficacy of a meal replacement diet plan compared to a food-based diet plan after a period of weight loss and weight maintenance: a randomized controlled trial. Nutrition journal, 9, 11. https://doi.org/10.1186/1475-2891-9-11

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