Some potential issues: First, the write up does not say if their study found a statistically significant difference between weight losers on the 'genetic' diet and those not on the genetic diet. They also do not define high carb and low carb. And just because someone digests fat better does not mean they will gain weight eating fat if their system ends up feeling satiated faster. Personally, I think the satiation factor is huge for weight loss. And if you digest fat better, that may mean your system is designed and adapted to eat more fat and therefore, it might actually be healthier for you and put your system in balance. To say you should eat more of what you are NOT designed for seems to me to be intuitively incorrect from a health perspective.
To me, the other big issue for weight loss is how the body processes and stores or uses the calories you eat. So a gene that gives a tendency to store carb as fat might be more of an issue is you already have too much 'storage.'
And on to another issue about gaming the system. If the majority of people are considered to be gene adapted for lower carb, then basically in the entire study, there will be more people told to eat low carb than any other diet. THis could automatically increase their chances of getting positive results by basically having near half the people eating low carb.
PLUS. THey don't say what their control group was. DId the control group just continue eating as a normal SAD eater or were they put on some other diet? Even a higher carb diet of healthy food is probably going to work better than most SAD diets.
I am suspicious of this because they are obviously trying to sell a product and are probably spinning the data accordingly. Plus they don't give any details to allow us to accurately assess the quality of their data.
