Older athlete health: does exercise trump diet?

As someone who takes training and performance seriously, you’ll no doubt be aware of the importance of nutrition. The importance of healthy eating patterns for athletes cannot be overstated. For most athletes, for most of the time, getting the dietary basics correct will not only make training goals more achievable, but will also be guaranteed to improve general health and well being, with less susceptibility to illness and injury.

Different people, different responses

As to what constitutes the fundamentals of good healthy diet for athletes, this is something we have covered at length in previous SPB articles (readers are directed to this in-depth article for example). However, what has been very clearly demonstrated in numerous studies is that diets containing too many calories, high amounts of saturated and processed fat and sugar/refined carbohydrates are major predictors of obesity, insulin resistance and diabetes, and disordered levels of blood lipids (increasing the risk of cardiovascular disease) in the general population^(1-3).

While the evidence for a poor diet leading to excess body fat and poor metabolic markers of health in the general population is overwhelming, when we look at this issue on a person-by-person basis, there are plenty of exceptions. Let’s face it, we all know someone who can fill their face day after day with calorie-laden, fatty sugary foods and yet not put an ounce of extra fat on – something that can be frustrating for those prone to gaining weight! But why is this so?

One reason is that there is a huge degree of genetic variability in metabolic functions, including those regulating the absorption, bioavailability, metabolism of nutrients and the metabolic function of organs/cells^(4-6). So for example, while a high-sugar, high-fat diet might make most people gain weight rapidly, there’ll be some individuals in the population whose metabolisms are able to respond to the excesses of calories, increasing metabolic rates so that no weight gain occurs.

Muscle mass and fiber type

Possibly even more important is that recent research shows that muscle mass and muscle fiber compositions play a profound role in how the body responds to dietary inputs^(7-9). Research has also recently reported that the total energy expenditure per kilo of lean body mass - and not nutrition itself - is the primary determinant of body composition during teenage years. This is evidenced by the fact that both normal weight and obese adolescents tend to receive increased total energy intakes, while at the same time exhibiting poor nutritional habits⁽¹⁰⁾.

These facts have led scientists to conclude that key markers of metabolic health such as blood lipids (cholesterol, triglycerides etc) is mainly determined by how humans metabolize their dietary intake, and not by the nutrition quality per se. In particular, individuals possessing greater proportions and sizes of oxidative muscle fibers (aerobic or ‘type I fibers) should also be characterized by healthier blood lipid profiles, compared to individuals with increased glycolytic (type II or non-aerobic) fibers, even if both follow similar nutritional plans⁽¹¹⁾.

The athlete’s metabolism

Given the above, it can be argued that since endurance athletes typically have higher proportions and sizes of oxidative muscle fibers^(12,13), and that their regular, high-volume endurance training leads to greater energy expenditure⁽¹⁴⁾ and the capacity to burn fat (via increased mitochondrial/oxidative capacity)⁽¹⁵⁾ the negative impacts of unhealthy high-fat nutrition on an endurance athlete’s body composition, blood glucose and blood lipid markers should be far less. Indeed, it’s even possible that these markers of health and ‘metabolic well being’ are primarily determined by training habits – ie that the exercise habits of an endurance athletes offers a huge amount of protection from bad dietary habits. If this is the case, it could be very significant for older athletes and fitness enthusiasts for whom well being and cardiovascular health are important motivating factors when training. But is this actually true? Well, new research by a team of Greek researchers has attempted to answer this exact question⁽¹⁶⁾.

New research

In this fascinating study, researchers investigated the protective effects of endurance training when consuming an ‘unhealthy’ diet. Published in the Journal of Clinical Medicine, this study compared what happened to middle-aged sedentary individuals and a matched group of middle aged endurance athletes undergoing training when they were both fed an unhealthy high-fat diet. The characteristics of the two groups were as follows:

• Sedentary – the 35 participants of the sedentary group were sufficiently inactive to not fulfil the ACSM’s recommendation for minimum active physical activity engagement. Average BMI in this group was 31.3 (overweight).
• Endurance trained – the 36 participants were runners who trained regularly and had participated in marathon and ultra-marathon races for at least ten years and were currently in training. Average BMI in this group was 23.2 (lean for this age group).
• The participants in both groups were of a similar age, averaging in the early 50s.
• None of the participants in either group had any major health issues or were taking medication relevant to metabolic markers.

For seven days, all participants were instructed to follow an unhealthy high-fat diet containing 30–40% of energy from and more than 10% of daily energy intake from saturated fats. Meanwhile 45–60% of energy intake was to come from carbohydrates and 10–20% from proteins. Importantly, the participants were instructed not to follow low carbohydrate/ketogenic diets (which are known to improve markers of metabolic health) and also to abstain from weight loss or maintenance dietary plans. Before and after the 7-day study, blood samples were taken and analyzed for:

• Trigylcerides
• Total cholesterol
• HDL and LDL cholesterol
• HDL/LDL ratio (higher ratios of HDL to LDL confer more protection against cardiovascular disease)

The participants’ 7-day food intakes were analyzed using standardized food diaries, while all participants also wore actigraph monitors (Garmin Vivoactive 3 ) to measure total activity and energy expenditure levels. The ‘before and after’ results were then compared for both groups.