Here is an awesome illustration of portion size if you are replacing your snack habits with nuts, but ALSO a perfect example of how a caloric surplus can sneak up on you and cause weight gain.
I know many people who snack on almonds at night, or try to have some walnuts in between meals to keep the junk food cravings at bay. This works in moderation, especially considering that nuts contain many benefits such as omega 3 fatty acids, vitamin E, magnesium and monounsaturated (healthy) fats. However, if left unchecked, they can add up along with the rest of your daily intake and take you out of the caloric deficit that you want for fat loss.
Though often viewed as a healthy alternative, they are super calorie dense and fats are the least satiating (satisfying) macronutrient. They taste super good and thus can cause people to binge on more than they should.
Like with anything, moderation and balance IS KEY. Take a good look at your days meals as a whole when considering whether or not you should even be snacking, healthy options or not. If you have room, nuts are a great way to get a modest amount of healthy fats in your diet. Don’t let sneaky calories fly under the radar and leave you confused at the scale.