Diet food, or less?

My cats were 20lbs and 16lbs 10 months ago. The bigger one is now 13.8lbs and the smaller is now 14.2 lbs. I feel like the smaller should have lost a lot more weight than that by now. She is getting 7/8ths of a 5.5 oz can per day. (approx 157 calories according to manufacturers info) Do I need to start her on a "diet" or "lite" canned food, feed her less, or give her more time? 

Edit: I've been slowly reducing calories over the last 10 months, did not start that low

Congrats on the weight loss! The big kitty might even be losing a bit fast, according to this article by Dr. Becker:

http://healthypets.mercola.com/sites/healthypets/archive/2010/03/03/weight-loss-for-fat-cats.aspx

Given that she's saying .5 lb to 1 lb depending on the amount they're overweight, a little under 2 pounds does seem a bit slow for the smaller kitty.

The article gives a lot of good points to consider. She's getting about the average amount of food volumewise, but what is that food made of? I've never been a fan of weight loss foods for cats because they tend to have lower calories, but higher carbs. I would give her a high protein diet. If you need less calories, consider a mixture of lower calorie but high protein food like Weruva. (Be careful - some foods like Weruva are only half the calories of your average cat food.)

This is weird but I've noticed that she will lose more weight if I feed her a higher calorie than normal for 2-3 days. So something like ~157 calories most of the time then ~180 calories for 3 days. (Learned this accidentally when I lost track of her amounts and accidentally fed her her brother's amount for 3 days, and found out today she's lost a little. This has happened before but last time I thought it was a coincidence.) I'm moving her from a food that has ~13% carbs to a grain free food that has ~8% carbs, so maybe that will help. 

The higher calorie food is lower in carbs, I assume? Could be that or it might be that her system needs change. People often hit a plateau when dieting and need a diet change in order to resume losing weight.

Raintyger said:

The article gives a lot of good points to consider. She's getting about the average amount of food volumewise, but what is that food made of? I've never been a fan of weight loss foods for cats because they tend to have lower calories, but higher carbs. I would give her a high protein diet. If you need less calories, consider a mixture of lower calorie but high protein food like Weruva. (Be careful - some foods like Weruva are only half the calories of your average cat food.)

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xcourtney3 said:

 
This is weird but I've noticed that she will lose more weight if I feed her a higher calorie than normal for 2-3 days. So something like ~157 calories most of the time then ~180 calories for 3 days. (Learned this accidentally when I lost track of her amounts and accidentally fed her her brother's amount for 3 days, and found out today she's lost a little. This has happened before but last time I thought it was a coincidence.) I'm moving her from a food that has ~13% carbs to a grain free food that has ~8% carbs, so maybe that will help. 

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That's very interesting about the calories and weight loss, @xcourtney3! I bet that cutting the grains along with upping the protein and reducing the carbs will help as you keep at the diet. Good luck!