New research done studying the effectiveness of both low-carb and low-fat diets was found to hinge on the quality of the foods eaten. While I definitely lean toward a lower carb style of eating, this study compared low-carb and high-carb diets of 37,000 adults over the age of 20. When comparing them in terms of longevity, they didn't find any great differences - until they compared the quality of the carbohydrates. The quality is what made a huge difference in mortality rates.
People who practiced low-carb or low-fat diets but consumed low-quality food actually had higher rates of premature death. That's common sense and should be a no-brainer! This research suggests that any increased longevity benefits conferred from either low-carbohydrate or low-fat diets may depend on the quality and food sources of macronutrients.
So any food plan or diet you choose to implement must have the quality and source of macronutrients clearly defined. I've said it before - you can become a vegan thinking it's healthier, but if you eat all genetically modified produce and refined grains, you will do harm rather than good. If you choose a ketogenic diet but eat conventionally raised animal products and foods that contain unhealthy fats, you will not be helping yourself.
Nutrition depends on nutrients. Choosing the highest quality of foods that provide the essential nutrients your body needs and recognizes should be the goal. This is precisely why many obese people are actually malnourished! They fill their bellies but are starving themselves of essential nutrients at the cellular level.