If you have health concerns where you need to address your saturated fat intake then obviously low fat dairy is an important consideration. For the average person, it is more important to modify how much dairy they consume rather than reducing the fat component, which often makes people, eat more anyway.
Dairy products like all foods, comprise of a breakdown in macronutrient content. They consist of carbohydrate portion – lactose, a protein portion – casein and a fat portion (a combination of saturated and unsaturated fats). Full fat milk on average contains 3% fat, 5% carbohydrate and 3% protein. Reduced fat milk on average contains 2% fat, 5% carbohydrate and 3% protein whilst low fat milk typically contains 1% fat, 5% carbohydrate and 3% protein. As the fat component reduces, the impact and weighting of the carbohydrate portion increases making the low fat product produce a higher glycaemic index and affecting your sugar levels (and eventually increasing the weight and fat percentage in your body).
The fat component in dairy is there for a reason. Consider for a moment when you are eating some yoghurt. First lets start with full fat yoghurt. When you eat it you probably can’t eat more than a few tablespoons due to the richness of the yoghurt. The fat content helps you control the quantity you consume as it provides increased satiety and sense of fullness. Now conversely, if you eat the low fat yoghurt, it is lighter and fluffier and you can often eat the whole jar. The quantity of what you consume is vastly different as without the fat (or with reducing the fat) you’re awareness of fullness is reduced. You end up eating more of it, having a huge load of sugar and then you wonder why you got a tummy ache! You’ve just flooding your digestive system with a huge quantity of lactose – often more than your body can breakdown. Reducing your intake overall is a much better strategy. Honestly reflect on how much you consume and you’ll realise that its probably a quantity issue more than anything else.