Is diet or exercise more important in combating obesity?

Sure diet on its own and its not very successful.

Exercise is more important,  because when incorporated with diet works 10 x better and easier then diet alone.

It is harder to exercise to lose weight.   Its hard to achieve a long term, daily  exercise commitment.  It is hard to find the right exercises to do that are easy and effective that you can fit into your busy schedule. Its hard to get motivated, Its some times humiliating so its hard not to be embarrassed.  Its hard to find some one that can issue the right exercises for weight loss with a high level of success and experience with the over weight and the obese. Its hard to find this type of health professional who will come to your home.  it is hard to find an exercise instructor that understands and is caring and not demanding.   Its hard to know how long to exercise for each day to lose weight every time.   Do the hardest thiing first, the exercise then incorporate the diet,  second. 
Your never hungry whlie you are exercising.
Exercise is the only way to get the highest increase in your metabolisum.  Diet alone and your metabolisum will drop to meet your new reduced food intake, then after a few days you stop losing weight so many think  why keep dieting ? and then drop out !   Then you go back to how you use to eat before  (  too much  food with high levels of fat,  protein and carbs  ) with now a new lower metabolisum, due to your diet only trial,  and less muscle density ( due to dieting without total body exercise )  and more flab.   hence the start of the yo yo diet.  Do this over and over again and you will get flabbier and flabbier, and with each diet only attempt ( yo yo diet ) its harder and harder each time to exercise.   

I only work with the over weight and the obese.

Diet and exercise has the same importance if you are trying to lose weight.
Research shows physical exercise on its own or diet on its own is not an effective weight loss strategy, they need to be combined. Weight loss will only be achieved if energy input (food and drink) is lower than the total energy expenditure ( activity of daily life and physical activity). Research shows that to lose weight you need to exercise more than 60-90 minutes/day at moderate intensity if energy ( food and drink) intake is not modified.

Losing weight is a long term lifestyle change and for this to be achieved and maintained it needs to be sustainable so good nutrition is important to sustain a lifelong active life while maintaining health and well being as weight is being lost and a healthy weight is being achieved.

This is a great question and one that's often answered without objective reference to the scientific research. Ask some fitness trainers and they'll tell you exercise is the most important factor. Some dieticians may hold the view that diet is far more significant. And yet a psychologist may say that all the stuff going on between your ears is perhaps the most important of all.

So who do you believe? I mean. they can't all be right - or could they?

Weight loss is a tricky business - and there is no magic formula or blanket approach that we can apply to everyone.

But here is a summary of what we know - when we refer back to the science:

Obesity is multifactorial - in any one person it is likely there are many contributing factors (ie: it's not just about diet & exercise). This is exactly why any weight loss program MUST be personalised and tailored specifically for the individual.

Some of these other factors that must be addressed include:

Genetics - we know that certain genes can make it more difficult for some people to lose weight. Identifying these first can help structure a tailored program.

Hormones - more often than not we find imbalances with hormones such as insulin, leptin, cortisone, oestrogen, thyroid or inflammatory hormones. When these are corrected, weight loss is much more likely.

Rest, Relaxation & sleep - It's not all about what you eat & how you move. If you're not getting sufficient rest to recharge your energy, weight loss will always be a struggle

Stress - High stress hormones will literally lock up your fat stores making it almost impossible to lose weight. Learning the skills to better respond to stress, both external & internal (ie: thoughts & emotions), will enable weight loss.

Thoughts, Beliefs & Emotions - quite obviously these play a major role in our ability to stay motivated and they are ultimately responsible for how successful we can become

Various other factors including your age, medical conditions and medications should also be considered.

It's unlikely we'll be able to solve the obesity problem by just looking at diet & exercise. We have to take a much broader approach & really look at all the factors - physical, mental & emotional. Just picking one or two will only ever provide short term benefits.

Are any factors any more important than the others? Well it really depends on the individual. Some of my clients say learning how to mindfully eat had the biggest impact. Others tell me that learning how to stop listening to the constant barrage of negative internal chatter going on in their minds has the most effect. And yet others say that learning how to take time out and manage stress was what helped most.

Sorry for not providing a definitive answer to your question. That's the nature of obesity I'm afraid.

Great question!

Before we begin discussing the subject of exercise and weight loss, let us first stipulate that exercise, whether through strenuous running or light walking, produces many positive effects. These include a lower risk for many diseases, improved mental health and cognitive ability, alleviation of many chronic pains and improved utilisation of oxygen by the cells. 

The truth is the effectiveness of exercise is dependent on the individual. However exercise has long been considered an integral component of weight management, but available evidence suggests that exercise alone is a relatively inefficient means for losing weight (http://www.ncbi.nlm.nih.gov/pubmed/16504621). 

While exercise does not add that much to weight loss initially, it is proven to help people maintain weight loss in the long term.

I would say that both exercise and diet are important and you need to do both of them simultaneously. You lose weight with diet and you exercise to tighten your musles and skin and help to maintain a healthy weight. If you just do one of them, I don't think you will succeed in losing weight.

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The American Heart Journal conducted a review with the following

"Available evidence suggests that exercise alone is a relatively inefficient means for losing weight. In contrast, regular exercise appears crucial in the prevention of weight gain and successful maintenance of weight loss, and in the fostering of cardiovascular health."