Almost everyone goes through periods of inactivity.  Blame it on the weather (hot or cold), vacation, job, family—there are interruptions in our fitness.  As we know too well, the surplus is deposited as “potential energy” around the thighs or mid section.  Sadly, most never use these reserve energy areas, which expand until you've had enough, and promise to diet or exercise. 

When researching Running and Fat Burning for Women with my wife Barbara, we discovered than most of those who decide to lose weight believe that exercise sounds like work, and choose calorie restriction.  Those who can focus well and handle deprivation can lose 5-15 pounds in a few weeks.  Without exercise, this is a temporary loss.  Research shows that almost all of the weight lost on strict diets is regained within the next 12 months.  A significant percentage of these cases actually gain back more than they lost during that period.  Here are some of the reasons why.

Weight loss doesn't mean fat loss. 

On many of the low carb diets, for example, the lower amount on the scale is primarily due to body fluid reduction.  The stored form of carbohydrate is called glycogen, which is used as fuel when running and other exertive exercise. This is also a reserve fuel source for the brain which is monitored constantly.  When you starve yourself of carbohydrate, glycogen storage is reduced to a level that triggers a starvation reflex.  Brain circuits remember.  But for every gram of glycogen lost, there are 4 grams of water which also disappear.  A 150 pound person can lose 5-10 pounds in 2 weeks.  But as soon as carbohydrate is consumed again, the glycogen and water are reloaded and the weight goes up and up…and up.  Low carb diets also tend to promote the consumption of fat, which is directly deposited on the body.  It is common for those on this diet to add to their fat stores, but they don't know this is happening because the water weight is being lost.  When carbohydrate consumption has resumed, the scales regularly provide a shock: more than before the diet started.

The Set Point

Our human ancestors who survived periods of famine and prolonged sickness had more fat on their bodies.  This genetic survival storage brain circuit programs us to add a little additional fat storage every year or two.  We can temporarily reduce the amount of fat on our bodies through diets, but the internal mechanism remembers. 

Starvation reflex

When we deprive ourselves of food, particularly food that we love, we initiate the “binge” response countdown.  At some point in the future when the banned food is around and one is alone, there's a great tendency to eat large quantities due to psychological deprivation.  When the total calorie consumption is extremely low, it is possible to burn off fat, while some essential nutrients are not ingested in adequate amounts.  If you're trying to lose the “spare tire”, food deprivation is counterproductive.  An appetite rebound is triggered over weeks or months after resuming normal eating, which leads to a total fat percentage that is higher than before the restrictive diet.

Gentle exercise with dietary change can help lower fat level

Aerobic exercise (walking, easy jogging, cycling, swimming, etc.) burns fat when the effort level is low enough.  If you are not huffing and puffing, and you can keep moving for more than 45 minutes, you are in the fat burning zone.  Exercise is the furnace that can burn fat off, and it produces many metabolic changes to keep it off.