Our Ask an Expert series is your opportunity to engage with world-class obesity experts at Obesity Canada.  Each month, we will solicit questions for some of Canada’s top researchers and health professionals to answer. This month, it’s month’s Dr. Jennifer Kuk, a kinesiologist specializing in exercise, activity, health and lifestyle behaviors. Dr. Kuk is an Associate Professor in the School of Kinesiology and Health Science at York University. She has published over 100 scientific papers, reports and chapters related to obesity, health and lifestyle behaviors.

Q1:  Hello Dr. Kuk, I am a 63 year-old female and have not been very active for most of my life. My weight has become problematic and I am eager to get it under control. I feel like I have 60 or more pounds to lose.  When it comes to exercise and activity, what would you suggest as the best approach for someone trying to lose weight, especially someone who is new to it.  Exercising is a bit intimidating, and I worry that it might be to late for me to start? 

Dr. Kuk: First, I will let you in on the fitness industry’s dirty little secret:  most people will lose only a few pounds with exercise alone.  It takes quite a bit of effort to burn off calories.  For example, the ballpark caloric equivalent of 3500 kcal (one pound of fat) is 10 hours of walking at 3.5 miles per hour. This means that if you follow the physical activity guidelines of 150 min/week, it would take you four weeks to burn off one pound.  That said, as a 63 year-old woman, regularly engaging in physical activity is extremely important for maintaining healthy muscle and bones even if you don’t lose a single pound.  In fact, you might notice that your pants will fit better and you will have more energy with regular activity, even if the scale does not budge.

Q2:  HI am a recent bariatric surgery patient and have lost over 100 lbs. I know being active and exercising is important to maintaining my weight loss, but I am curious — what are the most effective exercises?  I typically stick to cardio machines in the gym, is that enough or do I really need to start weight training, and as far as cardio goes, is there one that is more effective than others? 

Dr. Kuk: In terms of exercise, the most effective exercise is the one you will do on a regular basis long term…Full stop.

The most important thing is to recognize is that physical activity needs to be an integral part of your life, and enjoying your chosen physical activity is an important part of you continuing to do it long term and for your mental health.  I think we can all agree that we are unlikely to sustain doing things that we hate.  With that in mind, for weight loss maintenance, any activity that helps you burn calories and maintain/increase muscle mass is likely the best combination.  However, the jury is still out there on how to do this.  In general, the more vigorous the activity, the more likely you will build muscle, so this could be weight lifting, or more vigorous cardio exercises, sports or activities of daily living (i.e. shoveling all the snow we have gotten lately). Recent evidence suggests that high-intensity interval training may also be an option if you do not have cardiovascular concerns. In terms of how much you need to do, people who have successfully kept off weight long term using lifestyle methods do 30-60 minutes of activity per day.  This is not a trivial amount and, at the high end, far exceeds the physical activity guidelines. So, try to build physical activity into your daily routine and, hopefully, you can make it something that you look forward to every day for the rest of your life.

Q3: I have recently gotten back into my healthy lifestyle in an attempt to lose some weight.  I use an online food tracking program that has given me a calorie intake number based on my current weight and goals.  I try to keep in the 1200-1400 calorie range.  My question is about exercise and how this effects my required intake.  Should I be eating back my exercise calories on top of my set calorie goal?  The 1200-1400 already has a calorie deficit built in so exercising is only making that deficit bigger, I worry that by exercising I may be making the calorie deficit too big and cause harm, but I have had others tell me not to “eat back” my exercise earned calories.  What are your thoughts?

Dr. Kuk: It is tough to say without knowing your size (i.e., actual caloric needs), and how aggressive this calorie deficit is for you, but as with most things there are pros and cons of both sides.


– Eating back your calories will likely lead to slower weight loss. Slower weight loss typically has less muscle loss and higher muscle mass may be better for you in the long run for weight management, but the evidence for this is mixed.

– 1200 kcal is at the lower end of caloric intake and there may be issues with proper nutrition if you don’t eat a balanced, varied diet.  You may want to consult with a dietitian if you have the resources, particularly if you have a restrictive diet.  Eating back extra calories will give you a bit of a buffer and get all the nutrients you need.


– Not eating back your calories will likely lead to faster weight loss.  Individuals who can lose weight faster typically have bigger overall weight losses.  There are some studies that show that faster weight loss is related with better long-term weight management, but this is contradictory to the point above about muscle.  So, we are not sure whether faster or slower weight loss is better long term. Faster weight loss is related with a higher risk for gall stones, so slow and steady might be the safer option.

– It is very easy to overeat and eat back more calories than you burned during exercise.  Many fitness centers have ‘healthy’ snack bars, but make no mistake, many of these ‘healthy’, ‘organic’, ‘homemade’, ‘all-natural’ snacks are still packed full of calories. Often these calories are not listed as fitness centres are not considered chain restaurants and are exempt from menu rules.  For example, many ‘healthy’ fruit-veggies smoothies or juices have just as many calories as a can of Coke, and a single serving can be more calories than you would burn in a half-hour workout.

The opinions expressed in Ask the Expert are those of the profiled expert, and not necessarily those of Obesity Canada. Content does not constitute medical advice.