You may love your diet, but Somer says many don't lose weight due to "mindless eating."
"I had one client who put away 300 calories taste-testing while she was cooking dinner and then sat down and had a full dinner besides," said Somer.
So keep a diary. Write down everything you eat.
The average for one bite of food is 25 calories.
"Four mindless bites a day and you'll gain a pound in a month no matter what diet you're on," said Somer.
Then there are "yo-yo" dieters, who eat well during the week, then splurge on weekends. Or "sweet-tooths," who want sugar daily, and the "healthy eater," who avoids things like bad fats and white flour.
"People say, 'I only eat whole grains and I just had a turkey sandwich for lunch and that's all I ate.' But then when you follow them around you find out that they were nibbling on the Hershey Kisses at the office," said Somer.
They mostly eat healthy, but they may also eat large.
"If we enjoy healthy food, that's fantastic, but we have to pay attention to portion size," said registered dietitian Ashley Koff.
Koff says some of the best foods contain a hefty dose of calories, so portioning is crucial.
Try an ounce of almonds (about 22 of them), and one or two pieces of dried fruit (but not handfuls).
Yo-yo dieters often choose packaged foods to cut calories. Their mistake? Not checking serving sizes, like in a fresh juice bottle: There are two servings in some bottles. Or an energy bar.
"There's actually 400 calories in [this energy bar]," said Koff. "It is more like a meal.'
For sweets-lovers, Koff also suggests a sprinkle of chocolate chips in a bag of whole-grain cereal, rather than sugar-free treats.
"This particular cookie has trans fats and sugar alcohols, things that aren't going to be that satisfying," said Koff.
Then there's those known as "backloaders," a technique used to save calories by skipping breakfast, maybe even lunch, producing disastrous results by overeating later in the day.
"Our body needs us to break the fast in the morning, it needs the energy to get the metabolism going. There's no getting around that," said Koff. "Nine times out of 10, what happens is their food becomes entertaining and calorically dense in the evening."
The real deal on dieting?
"There's no perfect diet," said Koff. "There's what works for you that has bits and pieces that incorporates what you like, and it has to match your lifestyle."