Posted on 9 September 2021
Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.
Why is this research important: To lose weight, you need to be in an energy deficit – burning more calories than you consume each day. There are two main ways to achieve this: you can decrease your energy intake (eat less) and you can increase your energy usage (exercise more). But when it comes to fat, it’s not just how much you have, but where it is located that is important for health. When fat is stored around abdominal organs (visceral fat), it is more harmful to your metabolism than fat that is stored below the skin (subcutaneous fat). Exercise and dieting are both effective weight loss strategies, but do they affect fat distribution differently?
What did the researchers do: In this study, researchers performed a systematic review of 65 studies that measured subcutaneous, visceral, and total body fat before and after an intervention with exercise, dietary restriction, or both. Most participants in these studies were middle-aged, and most studies lasted for less than one year.
Key takeaway(s) from this research: Exercise appeared to be a more effective method for losing visceral fat than calorie restriction. For each kilogram of total body fat lost, the cross-sectional area of visceral fat fell by an average of 6.3 cm² for calorie restriction alone, 5.5 cm2 for calorie restriction and exercise together, and 8.8 cm² for exercise alone. However, there are some important caveats to consider when it comes to these results.
Firstly, the researchers were not able to perform a full meta-analysis, meaning that there was no attempt to calculate statistical significance of the reported effects. In other words, we don’t know the likelihood that the differences between different weight loss methods could have been due to random chance, so we can’t really draw any conclusions from these results.
Secondly, while exercise produced more visceral fat loss as a proportion of total fat loss, studies in which CR and CR+exercise were used still resulted in more total fat loss and more visceral fat loss overall because they achieved a greater energy deficit. Without statistical quantification, it is impossible to conclude that these strategies are more effective than exercise alone (note how CR+exercise achieved less fat loss than CR alone because the extent of CR was greater in the CR only studies.) However, it’s worth pointing out that simply reaching the highest energy deficit possible is still likely to be the most important factor in losing visceral fat.
Finally, almost all of the exercise studies included in the review used aerobic exercise as their intervention, so the results do not speak for the effects of resistance training on fat distribution.
Comparisons of calorie restriction and structured exercise on reductions in visceral and abdominal subcutaneous adipose tissue: a systematic review: https://doi.org/10.1038/s41430-021-00942-1