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MACRONUTRIENT BALANCE

There is some inter-conversion between nutrients such as protein being converted to glucose (gluconeogenesis) for release into the bloodstream, but under normal conditions, the capacity to convert one nutrient into another for storage is very limited. Also, humans have little capacity to ‘waste’ extra energy by burning it off. This process, which has been termed luxuskonsumption, is common in animals such as rats but is very limited in humans. Therefore, the examination of each macronutrient as a separate entity is necessary and is summarised below.

Fat. Fat is handled very differently by the body compared to the other nutrients. Body fat stores are large and not actively controlled and fat intake has no influence on its own use as a fuel (oxidation) and very little influence on appetite. Fat (from the diet or adipose tissue) is the energy buffer for the body in that it makes up the difference between what the body obtains from non-fat calories and what it needs to keep functioning. It is the last priority as a fuel. Fat is therefore not balanced at all and in a sense the body is ‘blind’ to fat, both in the diet and in the fat stores when it comes to balancing up its energy needs. Excess fat is therefore the most powerful dietary promoter of weight gain.

Energy balance and fat balance are essentially equivalent. This means that on a day when a person has eaten 200kcal more than they have burned, about 200kcal of dietary fat will be stored as body fat. If a person is 200kcal under, the body will pull about 200kcal of fat out of the fat stores to make up the deficit.

Table 5.1 shows how carbohydrate and protein intakes are fully balanced or regulated (suppress appetite and promote their own oxidation), alcohol intake is only half balanced (promotes its own oxidation only), and fat is not balanced at all. As originally proposed by Professor J-P. Flatt from the University of Massachusetts, a high-fat diet therefore tends to lead to a passive over-consumption of calories which may become chronic because of the weak or absent metabolic controls on fat balance.’

All this implies that a reduction of fat in the diet is all that is required for reducing body fat. There are certain advantages and disadvantages of this approach, as opposed to the old notion of calorie counting. Reducing fat, for example, doesn’t feel like ‘dieting’ and is therefore much easier than total food restriction. However, there is a perception that a low-carbohydrate diet is more effective because much of the weight lost is fluid which occurs relatively quickly. In a low-fat diet, the loss is slower but is more likely to come from fat than fluids. The low-fat approach also allows large volumes of food to be eaten with a minimum of restrictions, hence not resulting in the problems of hunger which occur with normal ‘diets’. In general, this whole approach leads us away from the traditional notion of calorie counting to one of ad libitum low-fat eating—a much more practical and effective approach to fat loss.

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. This entry was posted on Friday, May 8th, 2009 at 6:03 am and is filed under Weight Loss. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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