I wouldn't say that 's a problem.... your metabolism is increased.. you need more fuel.
Just make sure to eat clean. I had a huge salad for lunch with tuna..and it was only about 160 cals, but filled me up... it's about eating cleanly, and not eating empty calories..

taken from - http://www.dummies.com/how-to/content/eating-clean-for-dummies-cheat-sheet.html

The Basic Principles of Eating Clean
Eating clean involves not only choosing the right foods to eat but also avoiding all of the junk foods and processed foods that are so readily available. The keys to good health and proper nutrition are in the following principles:

Eat whole foods: Whole foods are foods that haven’t been tampered with, in the lab or the manufacturing plant. The foods you eat on this plan are straight from the farm: whole fruits and vegetables, whole grains, grass-fed and free-range meats, low fat dairy products, unsalted nuts, and seeds.

Avoid processed foods: Processed foods are any food that has a label. A label means that more than one ingredient was used to make that food. You don’t have to eliminate all processed foods (like whole grain pasta or natural cheeses), but if you can’t pronounce an ingredient on a label, don’t put that food in your shopping basket.

Eliminate refined sugar. Refined sugar provides nothing but calories. Other sweeteners can be used, but with all the good foods you add to your diet, refined sugar really has very little place in the eating clean plan.

Eat five or six small meals a day. By eating smaller meals throughout the day you can help rev up your metabolism and reduce the chance that you’ll eat some Funyuns rather than that whole grain cracker with nut butter and strawberries. You never get so hungry on this plan that you’ll feel deprived or feel the need to cheat.

Cook your own meals. Instead of buying meals in a box, cook meals from scratch. That’s not as hard as it sounds! Clean, whole foods need little preparation beyond chopping and sautéing to make satisfying, delicious meals your family will love.

Combine protein with carbs. When you do snack or eat a meal, make sure that meal is balanced. For the most satisfaction from your diet, and so you’ll be less tempted to eat junk food, combine protein with carbs or carbs and fat. This simple act will fuel your body and quash hunger pangs.

I've noticed this as well, thats why I'm trying to snack on super low calorie things, LOTS of lettuce, brocolli etc when I feel like turning to high calorie stuff. Probably because I'm burning much more on these workouts then previous Jillian Michaels ones.

I noticed the same thing. Hungrier than normal...even while on Phentermine. My weight has gone up two lbs since starting INSANITY last Monday. Not cool. I read that its normal for the weight to go up at first. Hoping this week is the come down.

This happens a lot! Makes sure you are taking measurements. People will lose inches, not pounds sometimes!