Cut fat not carbs to lose the love handles

The main point of this study is that it pitches science at fad diets and disproves assumptions that cutting out carbs will give a physiological edge in weight loss. But before we run off thinking the message is to totally avoid fat, pause to think.

The researchers are correctly cautious not to over translate their findings. They describe how by cutting out carbs the body uses its alternative fuel source - fat. Remember this is also delivered in the carb reduced diet. On the other hand, cutting back on fat meant the body went into negative fat balance. This was measured in physiological terms. The whole body measure (DXA) could not pick up any difference in body fat, even after 6 days. The authors also correctly acknowledge that in everyday life simple food choices mean the variation in diet composition will be substantial, so even if we see something under controlled conditions it may not be relevant to everyday life.

And there’s more. We know that not all carbohydrate in food is equally accessible by the body. Highly refined foods appear to deliver more than foods closest to their natural state. The same goes for fat, and beyond that, there is a big difference in the type of fatty acids that are delivered by fat rich foods. What really matters is the type of foods you choose to eat.   So this research is really interesting and adds a great deal to discussions amongst scientists. But for consumers, let's make sure it does not get lost in translation. We need to take this beyond the physiology of carbs and fat to food choices.

The best message at this point in time is to eat foods described in dietary guidelines that have reviewed the totality of evidence for their diet effects. These include foods that deliver carbs in whole food forms, such as vegetables, legumes, fruit, whole grains and yoghurt. It is also foods that deliver the right kinds of fat in a whole food, such as nuts, seeds, whole grains, avocados, lean meats, fish and culinary oils.

Long term weight loss is about healthy lifestyle. Keep active and don't eat too much - be your own scientist and hop on the scales. It's still a great measure of how you are going.”

This study only examined changes over 5 days and showed, as claimed, that there was more fat loss on the low fat diet over this period of time. However more changes will occur with time and the differences will disappear.

That is long term a calorie is a calorie – the body just takes a while to switch its metabolism to match what it burns to what it consumes and 5 days is not a reflection of what occurs long term. So there are no new findings from this study. The size is not a problem for a study like this.

This well-controlled study provides high quality evidence about what will occur metabolically if an obese patient follows exactly as prescribed a specific reduced fat or reduced carbohydrate weight loss diet for two weeks. However, these results cannot be simply translated to what would occur if the diets were prescribed during a sustained period of free-living, in which people have individual control over what they eat.

During free living, numerous factors such as appetite and food advertising, price and availability can play a role in regulating how closely people adhere to a prescribed weight loss diet. Indeed, such factors that influence how much and what a person eats are likely to have a greater impact on long term weight control than a relatively small metabolic advantage pertaining to a particular diet.

The basis of a good weight loss program is a diet that people can stick to, and this will vary for individuals!

This metabolic ward study was small and short because such meticulous monitoring is expensive and unsuitable for long-term study. It is valuable to explore the physiological effects of restricting fat or carbohydrate. Note however, that the authors' modelling from these results showed pretty close effects for body fat losses.

Ultimately, any weight loss plan needs to be healthful and maintained for life. That means looking at foods rather than concentrating on macronutrients such as fats or carbs. There are healthy food sources of both fat and carbohydrate that are much better choices than are currently being made. Healthy food sources of fat include oils such as extra virgin olive oil, nuts, seeds and avocado. Healthy food sources of carbohydrate include wholegrains, legumes, fruit, milk and yoghurt.

Sadly, in Australia, 35% of adults' and 41% of childrens' kilojoules now come from junk foods and drinks. These are high in both undesirable fats and carbohydrates and we should direct our attention to these rather than simply pitting fat against carbs.