Opinion: when it comes to purging after the Christmas excess, people should consider a tailored approach to peri-training nutrition

It is time to take stock after the Christmas excess and get back into eating less and moving more. Given the ever-increasing levels of overweight and obesity among Irish young and old, anything that acts as a springboard to do this is surely worth a punt and a more tailored approach to peri-training nutrition (PTN) may be in order

Eat less, move more

The notion of energy as a balance, where energy in (calories) needs to be less than energy out (activity) in order to achieve weight loss, has advanced. Research investigating the interplay between food quantity, quality and timing of ingestion relative to a specific exercise activity may provide opportunities to get more from the training you do.

Energy balance: energy in and energy out


The first consideration in a more mindful approach to fuelling training should be your intent: what are you hoping to achieve from the activity you are about to undertake? You might be hoping for weight loss, which is the most commonly cited reason for participation in physical activity. A more important question is what type of weight are you hoping to lose? Our bodies comprise of fat, lean, bone masses and water.

Typical body composition. Image: McGraw-Hill Higher Education

Those trying to lose fat mass should undertake different activity to those trying to gain lean mass. Those trying to achieve both fat loss and lean gain have a more challenging situation. In all cases, the role of nutrient quantity, quality and timing is paramount. (Note that calories are not even mentioned here!)

Increasing muscle mass 

The recommendations for nutrient intakes around resistance training (strength) are well established. The intention for most who undertake resistance training is to increase muscle mass and strength for functional benefits (or aesthetics!). We know that strength training is the most potent stimulator of muscle growth, and it is now well accepted that food intake around the training session has the potential to optimise this training effect. In essence, this means that consuming the right foods when you lift weights can give you better results than training in a fasted state. We are in a constant state of turnover when it comes to muscle. The interplay between activity and nutrition can swing the balance towards muscle accrual or loss.

Changes in muscle protein synthesis and breakdown in response to resistance training and feeding

The specific food constituents necessary to optimally stimulate muscle growth are high quality proteins. Proteins in meat, fish, chicken, eggs, dairy and legumes are not only a substrate for muscle growth, but also a driver. 

However, not all proteins are created equally. Proteins comprise of amino acids and the specific amino acid constituents determine the quality of the protein food. Branched chain amino acids (BCAAs) such as valine, iso-leucine and leucine are particularly potent stimulators of muscle growth, with leucine most effective in this regard.

I think the best graphic I have seen depicting the role of protein in resistance training is from Professor Kevin Tipton’s lab in Stirling University (below). The Lego worker represents the cellular signalling pathway, which is stimulated by leucine (red brick). Ingestion of BCAAs only, without additional protein to supply sufficient material to build muscle, provides maximal stimulation of this signalling pathway but leucine (caffeine for the worker) results in a smaller, at least less prolonged, response of muscle protein synthesis (A). Ingestion of a whole protein (or another source of all the essential amino acids) with ample leucine provides maximal stimulation (coffee for the worker) and sufficient substrate for complete muscle growth (B). 

Essentially, to get the most from a lift, train in a fed state. Aim to consume protein in or around the time you lift and ensure the protein is of high enough quality to provide the cellular workers with both material to build muscle and a stimulant to keep them working efficiently (like your mid-morning coffee break). 

Current recommendations for protein intakes around resistance training are to consume 0.33 g/kgBM of a quality protein (high branched chain amino acid composition) post training. There has been much debate as to the best time to consume this with previous research focussing on a tight window of opportunity to ingest protein post strength training for maximal effect. The anabolic window is open for much longer than was previously thought and the necessity to consume within a short time frame of training is no longer considered to be of great consequence

The importance of sufficient availability of protein as well as leucine to support complete synthesis of muscle protein following exercise. 

Reducing fat mass

The situation is less clear-cut for those hoping to lose fat mass. My exercise physiology colleagues could argue the merits of endurance, cardiovascular and high intensity training for optimal fat mass loss. There are many nuances to consider here such as activity type, intensity, duration, and frequency. There is still a lack of consensus but the experts currently seem to favour high intensity interval training (HIIT). 

However, a similar scenario is emerging with nutrient intakes around exercise to promote fat mass loss. Nutrition can help and hinder the cause. Exercising in a fasted or carbohydrate-restricted state has been investigated as a potential nutritional strategy that can modulate adaptations to endurance exercise at a cellular level. Carbohydrates are the preferred fuel source for exercising muscles. The reason for this is energy efficiency and the amount of oxygen required to burn different fuels (Fig 5). 

Fat oxidation increases from low to moderate exercise intensities and decreases as the exercise intensity increases further. For exercise of long duration, a return to fat oxidation it is inevitable as carbohydrate stores in the body are depleted.

However, research investigating the effects of exercising in a carbohydrate restricted or fasted state show promising results in terms of promoting fat mass loss. It also seems that skipping the usual staples for endurance training athletes, (carbohydrate rich energy drinks and a carbohydrate rich recovery meal like pasta or porridge) can prolong the fat-burning effect. 

The most common objections are the inconvenience of exercising fasted (which usually means getting up at 6am). However, this seems a small price to pay if you could theoretically continue to burn fat while you drive to the office if you postpone breakfast. Another objection here is the time it takes as moderate activity for 40 – 60 minutes is the current prescription. A more time efficient alternative may be HIIT. 

So what should you do?

The difficulty with nutrient prescription of any kind is that people do not eat nutrients - we eat food! Putting the research into practice can be confusing, so some final thoughts and food-based guidelines for improving body weight and composition are as follows:

- Eat less and move more

- Include strength as well as cardiovascular training

- Consider your intention with each training session and eat appropriately

- Eat a high quality protein (e.g. low fat dairy) when you do weights

- Consider the need for any carbohydrates (energy drinks, cereals or pasta) if you are aiming for fat loss

- Don’t restrict food intake excessively, you will lose both muscle and fat

If you are in doubt about the best approach for you, consult with a registered dietitian or registered sport and exercise nutritionist. Generic advice provided here should not replace advice specific to any individual. 

The views expressed here are those of the author and do not represent or reflect the views of RTÉ