Optimising Nutrition for Fat Loss

Nutrition and exercise are the cornerstones of attaining overall good health. Optimising nutritional intake can improve and accelerate recovery from exercise, achieve and maintain an optimal body weight and minimise the risk of injury and illness.

Often, people go on diets in an attempt to loose body weight, although in reality the aim should be to maximise fat mass loss and retain as much fat free mass (muscle, bone etc.) as possible. A reduction in body fat requires the achievement of an energy deficit, meaning we expend more energy than we intake; achieved by either reducing energy intake, increasing energy expenditure or combining both methods. An energy balance occurs when energy intake (energy obtained via all food and beverages consumed) is equal to energy expended through physical activity. Energy intake is derived from the breakdown of macronutrients (carbohydrate, protein, fat and alcohol) within our diet. Energy expenditure however is a little more complex; and includes the energy involved in absorption, metabolism and storage of the nutrients from the food we eat as well as the energy we spend as we breathe, as our heart beats and as our body cools and warms during exercise.

This article will look at the components that make up energy expenditure, followed by a simple method to estimate this. Finally, macronutrient proportions within the diet will be discussed with advice on how to manipulate macronutrient intake in order to maximise fat loss.

Energy Expenditure

A reduction in body fat requires the achievement of an energy deficit, either by reducing energy intake, increasing energy expenditure or combining both methods. Calculating an individual’s energy expenditure can be the first step in identifying the caloric needs in order to achieve an energy deficit.

An individual’s daily, total energy expenditure is comprised of:

• Resting energy expenditure (REE)

• Thermic effect of food (TEF)

• Energy expenditure of physical activity/exercise (EEPA)

REEis the highest contribution to daily energy expenditure and represents the energy needed to sustain basic life process such as breathing, heartbeat, renal function and blood circulation. This is thought to account for about 65% to 80% of total energy expenditure. TEF represents the energy required to process food including digestion, absorption and transport and can range from 5% to 30% of energy demands. EEPAis the most variable component and most easily altered via increased activity/exercise and accounts for 20% to 40% of energy demands.

Estimating Energy Requirements

Energy expenditure can be assessed via direct or indirect calometry which most often requires laboratory equipment. Alternatively, there are several calculations using derived formula that can be used estimate and individuals energy expenditure. The Dietary Guidelines for Americans(2005) and The Dietary Reference Intakesprovided estimate equations for men and women based on predictive equations based on the doubly labeled water technique used to estimate energy needs (fig.1).

Current recommendations suggest a moderate energy deficit of 500-1000 kcal/day below the estimated energy requirements (EER) is the most suitable approach for long term weight loss (NHLB, 2003). This equates to approximately a 20-40% deficit below EER. A more moderate deficit is recommended as it is more sustainable and may achieve better long term weight loss as well as resulting in greater loss of fat free mass (FFM) (Forbes, 2000). Consequently, if an individual with an energy requirement of 2500 kcal/day followed a 20-40% deficit this would result in a weight loss of approximately 0.45-0.90kg per week.

The Quality of Weight Lost

An important consideration when attempting to lose weight is the qualityof the weight lost. Weight loss from energy restriction alone has been shown to result in a significant loss of skeletal muscle which is unlikely to be reclaimed in the absence of resistance training (Strychar et al, 2009). A reduction in skeletal muscle mass is far from ideal as this will result in reductions in muscular strength and resting energy expenditure. Furthermore, skeletal muscle is the primary site for blood glucose disposal, thus plays a vital role in regulating blood glucose levels and preventing type 2 diabetes (Holloszy, 2005). It is therefore apparent that weight loss strategies need to protect against the loss of skeletal muscle and promote fat loss.

Exercise in combination with energy restriction has been shown to be more effective at losing fat mass and preserving fat free mass than just energy restriction alone (Weinheimer et al, 2010). When the exercise of choice is resistance training, all fat free mass may be spared, with the added benefit of potentially increasing fat free mass (Weinheimer et al, 2010).

Macronutrient Proportions

Many weight loss diets set macronutrient intake of protein at 15% of energy intake, fat at <30% and carbohydrates at 50-55% (Phillips, Zemel, 2012). Although it is reasonable to reduce energy intake with this ratio and promote weight loss in the short term, it has been shown that this diet is associated with low satiety and poor long term adherence (Sachs et al, 2009, Phelan et al, 2007, Foreyt et al 2009). Emerging evidence is showing that reducing the intake of dietary carbohydrates is of crital importance in both promoting greater weight loss and greater loss of fat mass (Gropper et al, 2018). Furthermore, an even more beneficial strategy is not only reducing the quantitiy of carbohydrates, but also to lower the glycemic load of the diet by favouring more low glycemic-index carbohydrate sources (Abete et al, 2010). The mechanisms supporting this effect are still relatively uncertain, but may relate to a lower blood glucose and insulin response (Feinman et al, 2007).

In addition to reducing carbohydrate intake, increasing protein consumption to levels above the RDA of 0.8g/per kg of body weight have been shown to be beneficial in the retention of fat free mass during an energy deficit (Williams et al, 2006).

When resistance training is combined with an energy restriction increasing protein consumption to levels of between 1.4-2.0g/per kg of body weight have been shown to be effective at not only retaining muscle mass but even increasing lean mass (Williams et al, 2006). The increased satiety and thermic effect observed with increased protein consumption explain the reason why higher protein consumption is so effective.

Conclusion

In conclusion, diets moderately high in protein (about 25% of energy, between 1.2-2.0 g/per kg body weight) and low in carbohydrates (about 40% of energy) with the balance of energy requirements from fat appear to be superior for weight loss. The preservation of skeletal mass is of vital importance during periods of energy restriction. This can be achieved by following the above advice in regard to protein consumption from the diet and including resistance training to the exercise program. Moreover, focusing on body weight rather than body composition when monitoring fat loss is a flawed approach as this does not recognise the importance of lean mass retention.

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