Want to Lose Weight? Which Is Best - Diet or Exercise?

For many years it has been thought that the best way to lose a significant amount of weight is by physical exercise. However, recent thinking advocates that diet is more important when trying to lose weight. Confused? Is it exercise or diet that is more effective at shedding those extra pounds?

The simple answer is both: 75% of weight loss is driven by diet and 25% through exercise. Although the answer appears straightforward the act of losing weight is not.

The human body has evolved to enable it to survive when there is a shortage of food, so when we restrict our food intake for long periods there is a reduction in the resting metabolic rate making weight loss slower and more difficult. In addition to this, levels of leptin - a hormone found in fat cells whose function is to regulate appetite - begin to fall. This reduction of leptin signals the hypothalamus to increase appetite resulting in the feeling of hunger.

The overwhelming feeling of a need to eat in this day and age, with food all around us, can lead to overeating and bad food choices (normally of the sweet and fat variety). An enormous amount of control is needed in trying to only consume low calorie, high protein food which will result in the feeling of being full and, consequently, stop the hunger pangs. Being on a low calorie diet is tough!!

However, it takes a net saving of 3,500 calories (calories eaten - calories burned) to lose 1lb (450g) of fat. That means, to lose 2lb a week, you need a net saving of 7,000 calories. That’s a net reduction of 1,000 calories per day.

This is hard to do through diet alone, but even harder through an exercise only regime. For example, someone weighing 185lb will burn 356 calories per hour when walking at a speed of 3.5 mph (17 minutes per mile). And the smaller you are, the less calories you will burn: someone weighing 155llb will burn 298 calories per hour when walking at the same speed.

So, without changing diet, that would take roughly 3 hours a day of walking to lose 2lbs in a week. That’s a chunk of time.

Stepping up the pace and running for an hour at 5mph will burn 300-400 calories per hour depending on size but this could be very difficult to maintain every day and still requires a significant time commitment.

Saving 1,000 calories a day through diet is a lot for most people but something like 500 calories per day may seem easier to do if you make sensible food choices, for example, cutting out processed and sugary foods, including protein with every meal, together with lots of vegetables and fresh fruit.

"Our studies show that you can eat up to a pound a day more food and still lose weight if you choose things that are low in energy density and water-rich."
Dr. Barbara J. Rolls, Professor and Helen A. Guthrie Chair, Director, Laboratory for the Study of Human Ingestive Behavior

Unfortunately, when you are on a diet, not only do you lose fat but you also lose lean tissue such as muscle and bone density. When you lose muscle you are losing a part of your body that burns calories. This is where exercise comes in; adding some form of physical activity becomes important as it helps to counteract the muscle loss and prevent bone density loss. Furthermore, including protein in the diet is important to counteract muscle loss as it is essential component of muscle building.

So, not only is a combination of physical exercise and diet required to contribute to the maths of a net reduction of, say, 1,000 calories per day but it’s also important when trying to lose fat yet maintain lean tissue mass.

One of the interesting findings in the Harvard Health Publishing article linked to above (and again here) is the amount of calories burned in the activities of many of our tahdah clients. Check it out. Rock climbing (ascending) is up there at 488 calories per hour. Orienteering is interesting too at 400 calories per hour. Perhaps the combination of exercising the brain and body in tandem leads to a higher calorie burn? We covered our client the National Navigation Award Scheme (NNAS) recently on how they are helping the UK become more active and that’s another great example of combining mental exercise with physical effort to maximise calorie burn.