Hi Cheyenne,
The 30 carbs is remnants of the Atkins or low carb diets. If you get your carbs down in the range of less than 30grams you get your body into ketosis mode, which many people choose to do even with bariatric program. This makes for fat burning and increased weight loss. The atkins diet focused on low carbs and fat and DID NOT RESTRICT CALORIE INTAKE. The idea is with ketosis happening and high protein you tend to be sated and without even counting calories you tend to eat less. It isn't always true though.
However, with the bariatric diet protein and calorie restriction are the two key points. Get your protein of 80-90 grams and keep your caloric input below 1200. Many people in doing this also restrict their carb intake as well probably making for better/quicker weight loss perhaps.
Regardless, if I am at 1200 calories a day and also having some reasonable activity, which typically places me below net 1000 calories per day, I am and do lose weight. Perhaps I would lose more weight in a shorter period of time if I also restricted carbs. For example, this month I am on track for losing 8 pounds during the month of February.
Last month I lost (January) I lost 7 pounds. So my rate of weight loss per month has slowed down compared to the initial months of November and December. That is OK by me. If I continue at a rate of say just 6 pounds per month, I will be under 200 pounds in another 4 months. Guess what? That is fantastic !!!
Perhaps I could restrict carbs and be under 200 pounds in 3 months instead of 4 months. You know what. I don't need to do that. If I get stalled and end up on a weight plateau, the way I do mix it up is to restrict carbs too for a few days up to a week.
I simply do not want to be so restrictive.
Best wishes,
Ralph