A personal trainer offers advice on diet and exercise that should start producing results in a month

There's something about summertime that brings a change in vision. Perfectly healthy people who see themselves as whole during the winter begin seeing themselves as parts, parts that won't fit neatly into swimsuits.

Too-big thighs, too-soft abs, too-flabby arms, too-big butts. Suddenly, when they look in the mirror, that's all they see.

It's a summer vision that drives people to their phones, punching up numbers to buy the latest ab-crunching, butt-busting gizmo advertised on TV.

But trainers such as Scott Martin of Big Sky: Fitness for the Human Race, say the belief that any one device or particular exercise can reduce one area of the body is misguided.

"If spot reduction worked, people who chewed gum would have a very skinny face," says Martin, who works at several Big Sky centres in Hartford, Connecticut.

We asked Martin for his recommendations of a routine that might have a visible effect in a month.

A comprehensive approach is needed, he says, covering diet, cardiovascular exercise and weight training or strengthening exercises.

"Eighty-percent of it is what you put in your mouth," says Martin. "You can exercise till you're blue in the face, but it won't do a whole bunch of good if you aren't eating wisely."

He favours eating small meals every two to four hours, which keeps the metabolism going, keeps blood sugar stable and helps prevent overeating.

"People think you should work out on an empty stomach, but the opposite is true," says Martin, who prefers free weights or body weight to build strength. He likes to employ multiple muscle groups at once. Such exercises work more efficiently, he says, because you get stronger faster and burn more calories.

He also suggests warming up with "dynamic flexibility" moves -- marching, lunging or doing other moves to warm up the body -- and ending the workout with traditional stretching.

Following this plan may not get you J-Lo abs or Michelle Obama arms in a month, but you should look trimmer.

"Everybody is a little bit different," says Martin. "Everybody has different metabolism."