NEW YORK (CBSNewYork) – If you’re having a hard time losing weight, your breakfast may be to blame.

While it’s hailed as the most important meal of the day, experts say it can derail your diet if not done properly.

“What you do first thing sets the tone for the day,” said Foodtrainers nutritionist Lauren Slayton. “If you have a sweet breakfast, you’re more apt to crave sweet things later.”

The same is true for carbs and fats. Oatmeal, for example, seems like a heart-healthy choice. But Slayton says it raises blood sugar levels. A study comparing people who ate plain oatmeal versus eggs found, “when people had oatmeal in the morning, they had 80 percent more calories later in the day.”

“So it’s not just the calorie and the makeup of what you eat, but what it then makes you do later,” she added.

The same goes for fruits. While rich in antioxidants, they alone will not fill you up. Add protein to feel fuller longer, along with other dairy like cheese – but too much cheese can cause bloat and long-term weight gain.

“The best dairy for me is dairy with probiotics, like a yogurt or there’s cottage cheeses that are what we call fermented,” said Slayton.

When it comes to fats, nuts are a good snack, but keep in mind: one handful of almonds has 162 calories.

Peanut butter is one of the best muscle-building foods post morning workout, but low-fat kinds can have added sugars and unhealthy oils, so grab the natural jar.

How about caffeine? Slayton says never get your boost from diet soda.

“The artificial sweeteners in diet soda wreak havoc on your body,” she said.

Instead, caffeinated coffee is the way to go – without sugary creamers.

So what should you have for breakfast? A lean protein, like eggs, with a small serving of fiber, like berries or an orange, and a little bit of good fat, such as nuts or avocado.