Most overweight individuals

evidently tend to choose exercise

as their first approach to weight loss.

When unrealistic hopes clash with reality,

the disappointment may lead to an abandonment

of weight-loss efforts altogether

as an exercise in futility, no pun intended.

Our false expectations may also give us license to overeat.

Our pie-in-the-sky notions about the power of exercise

may just be used to justify an extra slice of pie

right here on earth.

Some researchers warn that labeling menus

with calorie equivalents of exercise

could be counterproductive,

backfiring if people rationalize their indulgences

after a workout.

This concern has actually been put to the test.

Exercise psychologists took a group men and women,

put them on a stationary bike,

and had them cycle until they burned

either 50 calories or more than 250 calories.

Unbeknownst to them, the researchers

manipulated the machines to give false readouts,

such that in actuality

both groups burned the same number of calories.

They just thought they burned more or less.

Then, they were offered a meal 10 minutes later,

ostensibly to measure

the "effects of exercise on taste perception,"

but the real purpose was to covertly measure

how much people ate.

Those who falsely believed

they had burned off more calories

did seem to demonstrate a greater "license to eat,"

ending up eating significantly more calories,

mostly in the form of chocolate chip cookies.

After a workout, people may be tempted

to treat themselves for their sweaty sacrifice.

To prevent this kneejerk reaction

from undermining our efforts,

we should strive to make exercise less of a chore.

In a paper entitled "Is it fun or exercise?

The framing of physical activity biases subsequent snacking,"

a study is described in which individuals were randomized

to the same amount of physical activity

but just described differently.

Half were told they were going on a "scenic walk,"

and the other half were told

they were going on an "exercise walk."

Afterwards, researchers covertly measured

how much dessert everyone took at a subsequent meal.

Those in the movement-as-exercise group

reportedly served themselves

about 35 percent more chocolate pudding

than the movement-as-fun group.

This is all the more reason to choose activities

that are enjoyable,

such as walking with friends or while listening to music,

or watching a video on the treadmill.

Reframing exercise as play rather than work

may not only make for a more sustainable regimen

but may make us less likely

to consciously or unconsciously feel the need

to later reward ourselves at the buffet line.

Even just thinking about exercise

may compel people to eat more food.

Those randomized to simply read about physical activity

went on to serve themselves nearly 60 percent more M&Ms

than those in the control group,

adding up to hundreds of extra calories.

The researchers concluded: "simply imagining exercise

leads participants to serve themselves more food."

Expending energy through exercise

may not just psychologically predispose us to eat more

but may physiologically make us hungrier.

We evolved in the context of scarcity,

so our body places great value

on rapidly replenishing lost fat stores.

This helps explain why the average weight loss

with exercise training

is only 30 percent of that predicted

based on the number of extra calories burned.

Calories in versus calories out

can be complicated by the fact

that changes on one side of the equation can affect the other side.

In other words, we can work up an appetite.

Carefully controlled studies

show that caloric intake tends to rise over time

to match any increase in caloric expenditure,

making significant weight loss through exercise alone

remarkably difficult.

This doesn't happen over a day or two.

After a workout,

there may not be an immediate increase in hunger,

but averaged over the week or weeks,

our appetite does tend to increase to balance out

most of the extra calories we've been burning.

This calorie compensation isn't perfect, though,

so we can end up with a net loss in body fat,

particularly at higher exercise levels.

So, the secret to weight loss through exercise

may be sheer volume,

at least 300 minutes a week

to achieve appreciable fat loss.

This regulation of our appetite through activity

works in both directions.

Just as there exists a higher level of exercise

where we can start to outpace our appetite and lose weight,

there's a lower level of exercise

where our body loses the ability

to sufficiently downgrade our appetite,

and we gain weight.

This sedentary zone where our appetite

becomes uncoupled from our activity level

appears to start at around 7,100 steps a day.

So, let's say you start out as a really active person,

chowing down on nearly 2,900 calories a day,

and, for whatever reason, have to cut back on exercise.

You'd think you'd gain a lot of weight,

but you're surprised that you don't.

Basically, no increased odds of gaining significant body fat.

What happened?

With your drop in exercise came an inadvertent drop in appetite.

But there's a limit to how far our appetite can drop.

Once you cross that threshold,

once you dip below logging at least 7,100 steps or so

a day on your pedometer,

your appetite doesn't slow much further to match,

and the pounds can start to pile on.

Your body tries to keep your weight steady

by adjusting your appetite,

but we just weren't designed

to handle such extreme low levels of movement

that sadly characterizes most of the U.S. population.