One of the criticisms of GL will be the fact that we can relax into thinking we can have high amounts of low gl foods that may also be high in calories e.g. Proteins, nuts,seeds etc.
If you are following Holford, using his menus etc and really watching the portion sizes then you should be ok. When you make up any of his recipes the portions are small but more than adequate.
I followed holford's plan but found losses stalled unless I watched the portions. I also found trying to remember how many gls this or that had was confusing. I decided to overlay his low GL plan with calorie tracking just until I could visualise correct portions, not obsessively.
This has worked well for me for almost two years.
At the end of the day, no matter what food plan we follow, calories in must be less than calories out in order to achieve weight loss. Most of us at one point or another have used calorie counting and this is probably why we keep an eye to them whilst choosing low GL foods.
See how you go and if the losses are stalling then consider counting the cals of your low gl foods for a week or two.