Vigorous or regular sexual activity will not yield a sexier body as only a meager 21 calories are burned, an expert said Wednesday in a conference that sought to debunk myths on weight loss.

Philippine Society for the Study of Overweight and Obesity (PASOO) Board Director Dr. Robert Mirasol said sexual activity lasting for six minutes would only burn 21 calories, not enough if one eats a calorie-rich food such as burger that is approximately 272 calories.

"Even if you have sex six times a day...but it's better than just watching TV where you will burn only seven calories," Mirasol said in his presentation.

The weight management expert also denied that small sustained changes in food intake or activities will lead to weight loss. Instead, he recommended large change in energy expenditure and large reduction of food intake.

"It's the volume of food we are eating that will change our weight," Mirasol said.

"Large rapid weight loss is associated with poorer long term weight outcomes," he added.

The doctor also warned against frequent snacking saying it also contributes to weight gain.

Eating too much fruits may also make one fat because it is the volume of food that brings in the number of calories in the body.

Obesity is the condition wherein there is too much fat in the body. Fat is measured through waist circumference, waist to hip ratio and through Body Mass Index that is calculated by dividing one's weight with his or her height.

The Normal body mass index is 18.5 to 24.9 kg/m2 and overweight index begins with a BMI 25.0 to 29.9. Obesity class 1 is 30 to 34.9 and extreme obesity is a BMI of more than 40.

Doctors are alarmed over the rise of obesity in the country.

Twenty-seven out of 100 Filipinos are overweight, Mirasol said. This means many are at higher risk for hypertension, diabetes, heart problems, stroke and cancer. Mirasol also warned that obesity makes a person prone to gall stones, reproductive disorders and obstructive sleep apnea.