Is Diet or Exercise More Important For Weight Loss?

When I am lecturing on weight loss, I always survey the audience, "What's more important, diet or exercise?"

About 30% raise their hand for diet, about 40% for exercise, and the rest try to say both or don't raise their hands at all.

Weight loss is all diet! That's right. You can not outrun a bad diet. And you can't outlift one either, if you are into weightlifting. It's just not possible. Sure, the two can work together, but the majority of weight loss comes from diet alone.

Recent studies have shown that the more you exercise, the more your body will reduce your metabolic rate. Your body can lower your metabolism by 28% if needed, and if you are obese, you can have a 50% reduction in metabolism. So exercise can be a double edged sword. More on this later.

The exercise part can help you look different in the end, once you have adjusted your diet and lost weight. If you lifted heavy weights while dieting, you will look nicer and more toned. If you ran or did cardio, you will look very lean, but could also end up skinny fat. We will get into this more later.

In case you need a visual, look up! Weight loss is 97% diet!

Multiple studies have been done on this and you can watch my 1.5 hour lecture on YouTube (DrAlo.tv) for an in depth review of all relevant exercise studies. Search for my "Exercise Research Review".

The Journal of the American Medical Association published one such study. Here are the results in graphic format from the study. You can watch that video if you want more exercise research.

Figure: 6-month weight loss and metabolic slowdown in 48 overweight adults randomized to four groups. Redrawn from Heilbronn LK et al., JAMA 2006 (abstract).

• Left panel: % of body weight lost. Diet only lost 10.4%, diet plus exercise 10.0%, the very low-calorie diet 13.9%.
• The diet plus exercise group cut only half as many food calories and made up the rest with workouts, and still did not lose more.
• Right panel: in every dieting group the body burned 117 to 135 fewer calories a day at rest than its new size predicted. That is the adaptation I talk about.

As you can see from the above chart, the group that did "Diet Only" lost more weight than the group that did diet and exercise. This is due to many different reasons. Firstly, in some people diet increases appetite. Another reason, is that some people may eat more if they exercise thinking it's ok to eat more since they are exercising, i.e. human behavior. Other reasons are the body's multitude of adaptation mechanisms. We dive deeper into these topics later.

Take a look at the study below. Adding exercise or "depending on exercise" to cause the majority of your weight loss, will not work. So many studies have been done on this. I will post some below and highlight the conclusions, you can go through them on your own.

Related Diet & Nutrition Posts

Want to understand what actually works for weight loss? See these related posts:

• Why You Can't Outrun Your Diet – How exercise is limited for weight loss
• Lose Weight Eating Foods You Enjoy – The practical approach to sustainable weight loss
• Dr. Alo's Dietary Guidelines – The evidence-based framework for eating