Dr Sam Decombel is the chief operating officer of genetic research and development company MuscleGenes and has a PhD in Genetics from the University of Birmingham. She is based in Oxfordshire.
Breakfast is the most important meal of the day, right? A message perpetuated by health agencies around the world for many years, it seems that no matter what new diet fads emerge, the one thing that stays constant is the respect that breakfast holds in the public consciousness.
Yet some of the most recent research emerging on meal timings is changing our perception on the way in which we eat. While you no doubt understand the importance of what you eat, have you ever considered how when you eat it might impact on your muscle-building and weight-loss goals?
At MuscleGenes, before we are able to agree nutritional recommendations and promote any major changes in dietary habits, it is important that we first review the scientific evidence behind them. This is why we’re currently taking a closer look at fasting as a dietary option on our plans.
With celebrity proponents including Hugh Jackman and Dwayne ‘The Rock’ Johnson, intermittent fasting is the latest dieting craze to sweep Hollywood. So what is it? Not so much a traditional diet as a change in dietary pattern, intermittent fasting involves periods of eating very little or nothing at all, followed by periods of feeding. It doesn’t necessarily require daily restriction of calories either, unless weight loss in your primary aim.
A number of different ‘types’ of intermittent fasting diet have evolved over time. These range from the Leangains (16h hours of fasting; eight hours of feeding) and the Warrior (20 hours fasting; four hours of feeding) diets to more complex alternate day fasting plans such as the 5:2 diet of two non-consecutive days a week spent fasting on a low caloric intake – 600 calories for men, 500 for women – with other days spent eating as normal.
Is there any evidence to suggest any of these diets work? If so, which would be the best one for you?
The rationale behind intermittent fasting is that it is characteristic of the diet patterns of early humans. From an evolutionary perspective, our ancestors would often find themselves in ‘feast or famine’ situations: an abundance of food one day, and none the next. The assumption goes that as a species we are optimally evolved to cope with these fluctuations in our energy stores, and therefore replicating these conditions will lead to the best outcomes from a health perspective. That’s a nice, neat explanation, but does it stack up?
Much of the early work on intermittent fasting was based on animal studies, and the amount of research supporting its impact is certainly significant. Multiple studies on mice have shown that periods of fasting lead to reductions in fasting glucose and insulin concentrations, indicating a positive impact on insulin sensitivity, which is a significant factor in metabolic health.
What’s more, with lower insulin concentrations, lipolysis – the process behind the breakdown of fats into free fatty acids for use as energy – is less inhibited too, resulting in increases in fat oxidation. On top of this, the animals had reduced body weight, lower cholesterol and triglycerides, reduced levels of pro-inflammatory cytokines and, importantly, they lived longer.
Even better, in studies where the animals were allowed to consume as much as they liked in the feeding period – and as a result caloric intake was not reduced and weight was maintained – the researchers still observed these positive benefits on metabolism and longevity, suggesting the most likely mechanism behind the effect is the alteration in insulin sensitivity rather than any weight loss per se.
Interestingly, studies in humans suggest that on a fasting diet we are better at moderating what we eat in periods of feeding than mice, and very often consume fewer calories than on an ‘average’ day as a result, inevitably leading to weight loss regardless.
But can we expect to see the same long-term health effects in humans that we see in mice studies? The short answer is yes, and data is now available do support these benefits being transferable to humans.
There are an ever-increasing number of studies (the majority, granted, in overweight or obese individuals) that demonstrate intermittent fasting leads to lowered weight, lowered cholesterol, and improved blood pressure, as well as improvements in a range of cardiovascular disease risk factors, including insulin sensitivity. It’s even been shown to reduce the effects of asthma in overweight individuals.
Most of the studies on those of a healthier weight are related to religious fasting, such as that which occurs during the month of Ramadan. The results from these studies are just as promising: reduced pro-inflammatory cytokines, reduced body fat percentage, and reduced blood pressure. Unfortunately for these individuals these positive effects reversed back to pre-fasting values 30 days following the end of the fasting period, but this only further supports the hypothesis that it is specifically intermittent fasting that led to these positive impacts on the body.
But what about in terms of performance? Will your training suffer as a result? There are now quite a number of athletes, and in particular bodybuilders, that are taking up fasting because of the perceived benefits.
From the studies available it seems to be a wise choice. One study of elite male power athletes showed no negative effects of fasting in terms of anaerobic power and ability to clear lactic acid, when the fasting was done in a regular manner.
Increases in muscle mass have been observed because of elevations in growth hormone and improved insulin sensitivity. When combined with exercise, intermittent fasting has also been seen to lower leptin (the hunger-inhibiting hormone) and increase adiponectin (a protein involved in regulating glucose levels, as well as fatty acid breakdown), indicating elevated fat metabolism.
So, should you train fasted? There is limited evidence that fasting prior to resistance exercise increases the response of anabolic signalling in the muscle following feeding post-workout to a greater extent than when beginning in a fed state. This suggests performing resistance training prior to the start of a feeding period may lead to greater gains in muscle mass, though more research is needed in this area for clarification on this effect.
Don’t think you can eat what you like during non-fasting periods – your macronutrient ratio has still been shown to be critical to making these gains. If you’re training in a fasted state, you need to ensure this is followed by the start of a feeding period, and that you take in plenty of protein post-training. Without it your net protein balance will remain negative, which is obviously not good for muscle building.
You might even want to consider supplements such as BCAAs to prevent protein catabolism and aid muscle protein synthesis. The ideal proportion of carbs to fats that will work best for you will be genetically determined, but in general it’s a good idea to consume a higher proportion of carbs than fats on workout days, with the reverse on rest days.
If building endurance is your fitness aim then higher-carb meals, especially following training to aid glycogen replenishment are ideal. Moderate to high GI foods, such as rice, potato and pasta, have been shown to replenish muscle glycogen most quickly.
Despite the potential benefits to performance, I would recommend sticking to fasting mainly during training periods, with any competitive events undertaken in the fed state to ensure you have adequate fuel to go the distance. There is some evidence that the effects of short-term fasting prior to performing high-intensity exercise can lead to reduced time to fatigue.
Is fasting for you?
So could a switch to intermittent fasting be for you? Despite our natural inclination to think of fasting as a difficult diet to stick to, the evidence so far actually suggests that people find it easier than more traditional caloric restriction diets. Despite this, there are some people for whom fasting is not an ideal option.
Women in particular may find that fasting can upset their natural cycles and in extreme cases impact fertility, so should be more cautious and use shorter fasting periods where appropriate. Fasting should be avoided altogether in pregnancy. Another group who should refrain from this diet pattern are diabetics. Despite the clear benefits to insulin sensitivity discussed above, diabetics are not well-suited to coping with large swings in insulin and glucose levels and need to maintain a more consistent food intake. Finally, fasting is not an approach I would ever recommend applying to children, who have much more complex nutritional needs than adults.
If you do decide to give fasting a go, the way in which you should approach it is very much about personal preference, and what is likely to fit best with your lifestyle because almost all intermittent fasting regimes have been shown to provide benefits. Consider introducing it slowly over the course of several weeks rather than going all out to from day one, and make sure you drink plenty of water during fasting periods to prevent dehydration.
Timing-wise, coordinating feeding periods with your circadian rhythm prevents detrimental alterations in your natural body clock cycle, so avoiding eating too late at night, and taking advantage of overnight fasting periods while you sleep is highly recommended. In active individuals, the post-workout meal should be the largest of the day, containing around 50% of the day’s calories.
Break your fast
So, back to where we started, what about breakfast? Bearing in mind my earlier point about personal preference, skipping breakfast and starting the feeding window around midday works well for most because it avoids the morning spike in cortisol, which can lead to a greater increase in insulin release following a meal, and hunger soon after breakfast. It also ensures you can eat dinner at a sensible time in the evening, reducing the impact on your natural circadian rhythm and reducing the chance of cravings, which are more likely to occur during the evenings.
The observation that people who skip breakfast are more likely to be overweight or have diabetes than those who don’t might be sound, but it is an example of correlation almost certainly not implying causation. In other words, individuals who skipped breakfast in these surveys usually tend to smoke more, drink more alcohol and take less exercise too.
If breakfast works for you though, go for it. We are all built differently after all and no diet is a ‘one-size-fits-all’ solution. You are unique, and you need to find the right solution for you.