Exercise is meant to help you get into shape by burning up calories stored as body fat. Burn around 500 calories more than you eat each day, and you’re on target to lose a pound of fat a week. That’s what the math tells us.
But many clients struggle to burn even 200 to 300 calories in a training session. When followed by a cake or muffin that tips in at 400 calories later in the day, the net result is a 100 to 200 calorie excess, which will cause body fat gain rather than loss. What’s worse, the client blames his trainer – you – that his program is not working when he doesn’t see results on the scale or tape measure. Sound familiar?
If only clients could keep their mouths shut after a training session... and keep their calories down. Unfortunately, weight management is more than a simple calorie numbers game. It’s a complex physiological process that centers around the human body’s biological drive for homeostasis. Put simply, your body tends to compensate for an attempt at reducing it’s energy stores. You may know this as the “set point theory.”
That’s why for some people, exercise may stimulate appetite and to a level which results in increased food consumption and complete compensation of calories burned up in workouts. But how do you know you’re at risk of the exercise-appetite drive?
Who’s at Risk?
Most research on the appetite-stimulating properties of physical activity shows that, at least in the short term (up to 14 days), appetite does not increase enough to cause a drive for full compensation of the energy burned during exercise. This is good news and means you can keep on promoting the same beneficial calorie burning, fat loss messages about exercise.
However, for some individuals, you may want to tweak your message to include an alert about the potential for exercise to stimulate appetite. The challenge is, we don’t really know who may be more susceptible to the exercise-appetite drive. Research studies are conducted on groups of people, with each individual having a different biological response to exercise that is hard to predict.
For example, a September 2007 study published in the International Journal of Obesity examined the effects of five 500 calorie exercise sessions per week for 12 weeks on 35 overweight and obese sedentary men. This program accumulates 3500 calories a week, which is equivalent to that magic one pound of body fat.
Weight change was highly variable and ranged from a loss of 14.7 to a gain of 1.7 kg. To examine why some men did fantastically and others not so well, the men were classified into two groups: Noncompensators, who lost around 6 kg, and Compensators, who only lost around 1.5 kg on average.
Energy intake increased by almost 300 calories a day in the Compensator group but decreased by 130 calories in the Noncompensator group. Subjective hunger rating also increased for Compensator but not for Noncompensators.
Previous studies have also shown huge variations in response to exercise, so what’s going on?
Searching for Answers
Scientists have only really just started to untangle the ball of biological wires that may reveal a clear mechanism to link exercise and appetite. However, some potential chemical culprits have been identified.
In a May 2007 study in the Journal of Endocrinology, 12 normal weight volunteers exercised for 60 minutes at 65 percent of their maximum heart rate, then had levels of gut hormones measured a few hours later. Exercise increased levels of peptide YY, glucagon-like peptide-1 and pancreatic peptide, which are all chemicals known to suppress appetite. It’s possible that, in some people, the levels of these hunger buster hormones fail to respond positively to exercise.
A longer term reduction in body fat may also act to stimulate food intake. Levels of the hormone leptin, produced by fat cells, fall in tandem with body fat. It is thought that leptin is the master regulator of chronic food intake and falling concentrations are a subtle trigger to munch more to rebalance body fat levels.
What Else is Happening?
Another explanation is cognitive calorie compensation, which means that exercisers may allow themselves to eat more as a reward for being active. This has been observed more in women than men, with one study showing that the energy deficit induced by exercise was completely “wiped out” when followed by a high fat lunch.
It’s also worthwhile checking for a decline in daily incidental activity. This can occur if exercisers decide to conserve their energy for workouts or simply feel they can be less active because they “go to the gym.”
Perhaps most importantly, a check on compliance to the exercise regime is vital to ensure enough calories are being burned for fat loss. Objective measures, such as heart rate or daily pedometer steps, give a much better indication of activity level than subjective reports of “doing workouts.” Just as the research has clearly shown that people tend to underestimate food intake, it also shows some people will significantly overestimate their level of physical activity.
When to Deal with Appetite
According to a 2003 review of exercise and appetite in the Proceedings of the Nutrition Society, “It is likely that the adoption of a more active lifestyle will have a number of consequences for appetite control.”
My experience has found that getting started on a set diet plan at the same time that fitness training begins is crucial for the initial results that boost motivation. After a week, it’s time to look at appetite because any calorie compensation or dietary blowouts due to cravings or eating triggers can break the program.
One objective of all my nutrition programs is to re-wire appetite and get the body’s natural appetite chemicals in sync. This can mean undoing a lot of bad habits, but the results speak for themselves.
I ask all of my clients to rate their hunger level immediately before they eat and when they stop eating. The idea is not to leave it too late to eat, otherwise a ravenous hunger will increase the chances of overeating. When eating, the challenge is to stop eating at a rating of “satisfaction” rather than full or very full.
Take Home Messages
Appetite management is the missing link between a diet plan, exercise and actual results. Here are some take home tips to fill the gap:
- Be alert to the exercise-appetite drive in yourself and your clients.
- Monitor your hunger fullness levels just as you would heart rate or rate of perceived exertion.
- If you are prone to unnecessary snacking, say a verbal, “STOP, do I really need to eat?” and wait five minutes before choosing to snack.
- Implement strategies to better deal with food cravings. For example, keep a healthy lower calorie snack like fruit with you at all times.
- If you tend to eat too much at meals, say a mantra to yourself such as, “It’s better to go in the waste than around my waist” and leave some food on your plate.• Integrate a nutrition strategy into any fat loss program you deliver.