Over the last couple of years, many studies have been published showing the benefits of calorie restriction and intermittent fasting. Should you try it? Benefits include weight loss, increased fat burning, muscle gain, improved energy levels, and improved insulin sensitivity and overall longevity.
CALORIE RESTRICTION
One such study, known as CALERIE (Comprehensive Assessment of the Long Term Effects of Reducing Intake of Energy) tested the metabolic effects of calorie restriction in a group of 53 healthy, non-obese volunteers who cut calories by 15% over two years. [1]
It found that calorie restriction decreases oxidative stress, a process that has been linked with ageing and age-related conditions such as Alzheimer’s and Parkinson’s, cancer, diabetes and others. [2]
One of the mechanisms for this improvement is that restricting calories can slow your basal metabolism. While we often think that, in terms of weight loss, a slower metabolism is “a bad thing”, by-products of metabolism do accelerate ageing processes. The study found evidence that calorie restriction enhances resting energy efficiency, resulting in less oxidative damage to tissues and organs.
INTERMITTENT FASTING
Another new study however, found that intermittent fasting diets were better than daily calorie restriction at clearing fat from the blood and thereby reducing the risk of cardiovascular disease. [3]
Researchers at the University of Surrey assigned overweight participants into either the 5:2 diet or daily calorie restriction diet. Those on the 5:2 diet ate normally for 5 days and then fasted for 2 days on 600 meal replacements, while those on the daily diet were advised to eat 600 calories per day fewer per day than their estimated requirements for weight maintenance.
The study found that those on the 5:2 diet cleared post meal fat more efficiently than those undertaking the daily diet, and also experienced a reduction in systolic blood pressure which further reduces risk of cardiovascular disease.
Dr Rona Antoni of University of Surrey, does acknowledge however that the 5:2 diet is not for everyone. “As seen in this study, some of our participants struggled to tolerate the 5:2 diet, which suggests that this approach is not suited to everybody; ultimately the key to dieting is finding an approach you can sustain long term”.[4]
TIME RESTRICTED EATING OR 16:8
Another approach to fasting and calorie restriction might be to limit the number of hours in which you eat. Studies with mice have found that those who had access to food at restricted times lost weight and improved a number of health markers, as opposed to mice given unrestricted access to the same amount of food. Time restricted feeding has been shown to treat and prevent conditions such as obesity, diabetes, fatty liver, high cholesterol and metabolic disorders.[1]
There are different ways of achieving time restricted eating but the “16:8 diet” is very popular. This is where you eat all of your food during an 8-hour window and fast for 16 hours overnight. The idea is not to cram 3 meals into that 8 hour period but to eat only 2 nutritious meals.[2] A less extreme alternative would be 14:10 – fasting for 14 hours, eating within a 10-hour window.
Again, this approach does not work for everyone, and as always with nutrition and diet, it’s a case of finding out what suits you as an individual and fits in with your lifestyle.
SUMMARY
The evidence is clear, fasting and reducing the amount we consume benefits not only our weight but all of our markers of health, while at the same time restoring our energy, vitality and motivation.
There are many books and articles on the subject. Invest in a good book and do it properly. Try:
Intermittent Fasting for Beginners: The Ultimate Weight Loss Guide incl. 5:2 Diet, 16:8 Diet and 30 Days Diet Plan Paperback – by Sarah Amber Patterson (Author)
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4255155/
[2] https://2mealday.com/
[1] Redman et al. Cell Metabolism https://doi.org/10.1016/j.cmet.2018.02.019
[2] Redman et al. Cell Metabolism https://doi.org/10.1016/j.cmet.2018.02.019
[3] https://www.surrey.ac.uk/news/fasting-diets-reduce-important-risk-factor-cardiovascular-disease
[4] https://www.surrey.ac.uk/news/fasting-diets-reduce-important-risk-factor-cardiovascular-disease
