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I have reduced my calorie intake and started strength training twice a week to help me lose weight. I've been at it for six weeks but my weight hasn't budged. Is this because I've built muscle?

Depending on how you're training, it is possible to gain some (muscle) weight. But it's also possible that your twice-weekly strength training sessions have nothing to do with why you haven't lost any weight.

Let me say first that you've done a smart thing by adding resistance training to your weight-loss effort.

Plenty of studies have shown that resistance exercise protects against the muscle loss that typically occurs with dieting alone. Research suggests that as much as 25 per cent of weight lost by cutting calories is from muscle versus fat.

Not good, since the amount of muscle you have is the biggest contributor to your resting metabolism, the number of calories your body burns at rest. Preserving muscle should be part of any weight-loss plan.

Back to your question. Is the reason you haven't lost measurable weight on the scale because you've gained muscle while simultaneously losing body fat?

It's not unlike a comment I sometimes hear from a client: "I've put on a few pounds, it must be my personal training." Maybe, maybe not.

How much muscle can you really gain?

To find out how much weight you can realistically expect to gain, early on, from resistance training, I turned to professor Stuart Phillips from the McMaster University Department of Kinesiology. He's a Tier 1 Canada Research Chair who's published dozens of studies on how exercise and weight loss affects body composition.

According to Phillips, studies show that women can expect to gain one to two pounds of muscle over the first four to six months of training while men can put on two to four pounds of lean mass during this time. (Women and men actually gain similar amounts of muscle relative to what they started with in the first place.)

Some people, however, will gain a lot more and others will gain less or nothing at all, likely due to their genetic predisposition.

But here's the caveat: Such gains in muscle weight occurred from doing resistance training three times a week. And the last repetition (rep) in the set pushed participants to fatigue. (A rep is the number of times you perform a specific strength exercise, such as a bicep curl; a set is the number of cycles of reps you complete.)

In other words, if your strength workout is light and/or less than three times a week, you're probably not realizing much, if any, muscle gain. So, if it's not muscle that's showing up on the scale, what's going on?

Diet blunders that keep the pounds on

If, despite a month (or more) of dieting and exercising, your weight hasn't decreased (presuming you were carrying excess weight to start with), it's time to reassess your eating habits.

If you're working out, it's easy to justify a second helping or a cookie (or two) after dinner. After all, you're burning those calories off in the gym, right? Don't be fooled. (More on this later.)

Or, perhaps in your new-found quest to improve the quality of your diet, you've forgotten that portion size matters also for healthy foods such as salmon, avocado, fruit, even salads. Oversized portions of good-for-you foods can be a hefty source of overlooked calories.

Another potential misstep: consuming too many calories from shakes and protein bars in an effort to recover from workouts.

Yes, exercise does increase protein requirements for muscle recovery, which begins as soon as your workout is over. While supplements are convenient, priming your muscles with protein can be done quite easily with real food.

There's certainly no need to gulp down a protein shake immediately after working out if you're eating your next meal within the hour.

And the benefits of loading up on protein before a strength workout remain to be seen.

Phillips, for example, isn't convinced that pre-exercise protein does much to boost muscle building. Post-exercise is the primetime to consume protein, he says.

Diet versus exercise for weight loss

If weight loss is your goal, be diligent about what you put in your mouth. Don't rely only on exercise.

It takes a lot of daily exercise to generate a calorie deficit large enough to influence the bathroom scale.

Since one pound of body fat stores about 3,500 calories, you'd have to burn off an extra 500 calories every day to lose one pound a week. For a 185-pound person, that requires roughly 40 minutes of running (6 mph), 70 minutes of very brisk walking (4.5 mph), or one hour of vigorous weight lifting.

Cutting 500 calories from your daily diet, on the other hand, is easier to do.

As Phillips says, "weight is lost in the kitchen while muscles (and fitness) are made in the gym".

Leslie Beck, a Toronto-based private-practice dietitian, is director of Food and Nutrition at Medcan.