The study tested low-carbohydrate

The study tested low-carbohydrate, low-fat and Mediterranean diets over a period of two years in 140 overweight people (88% men, average age 51). It showed that any one of the diets could effect cardiovascular benefit as long as a particular amount of weight was lost. This means that it is the process of weight loss, not what makes up the diet, that is responsible for the positive changes.

Over the two-year period, those who had lost 11 pounds had more improvement in their arteries than those who lost 7 pounds. Those who lost the most weight that also lowered their blood pressure from diet experienced the most benefit in terms of arterial improvement. Because participants who were already on blood pressure medication were left on them, the study was able to show that it was the weight loss related to diet, not the drugs, that were increasing the health of arteries. That is consistent with the following: better numbers shown on paper due to medications is not the same as having better numbers because you are actually healthy.
Weight loss is the key

In other words if you are taking blood pressure medication but not losing weight, then there is not much chance you are actually reversing the health of your arteries. Conversely, real cardiovascular improvement can be set in motion by naturally lowering your blood pressure through weight loss.
Bottom line

This is great news for overweight people. You don't have to lose all the weight to manifest an environment in your body that will start to mitigate the issue of heart disease. It means that if you just get consistently on track and maintain that consistency over a period of time, you can improve your health significantly. You will reach your weight goal sooner or later, however health benefits will begin to reveal themselves during the early stages of such an improvement effort.