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by Dr Abbi Lulsegged (BSEM)

Response to the article "Fasting diets may raise risk of diabetes, researchers warn"
(The Guardian, 20.05.18) by BSEM member Abbi Lulsegged

Dear Sir,
Thank you for the article, “Fasting diets may raise risk of diabetes, researchers warn” written by Robin McKie and published on 20th May 2018. We wanted to bring to your attention and to your wider readers, several caveats that are necessary in interpreting this work. The work was accepted as a poster/abstract at our recent annual European Congress of Endocrinology meeting. Firstly, the experiment was not performed in humans, but in a type of rat known as Wistar rats. This is an important point because, whereas animal models provide a basis for understanding human physiology and pathology, data obtained from experiments in animal models cannot be automatically extrapolated to humans. Papers have been published encouraging caution particularly in animal models of obesity[i]. Additionally, the rats were fasted for 24 hours every other day – proportionately one wonders if the duration of the fasting period might have been too long. We do not know if this might have been interpreted as a “stressful” event for the rats, moving the intervention from a possible beneficial event to a harmful one. Stress can promote the release of key hormones such as cortisol and ghrelin which promote weight gain and hunger respectively.
 
Secondly, and more importantly, we have intermittent fasting studies performed in humans with excellent outcomes. In one such study of overweight women who fasted two days a week (on the days, they fasted they restricted their calories significantly but did not stop eating), there were significant reductions in insulin levels – a highly desirable finding for preventing diabetes mellitus compared to the group of women who had simply restricted calorie intake[ii]. Crucially, human studies of intermittent fasting in which no calories are consumed – either continuously or intermittently show improved metabolism and weight loss.
 
Thirdly, rather than intermittent fasting promoting diabetes, for reasons partly alluded to above amongst others, this form of diet especially when combined with a reduction in sugars and total carbohydrate intake can work powerfully to control diabetes in the early stages preventing progression if not reversing it in select cases.
 
Ultimately, research into obesity (for the purposes of finding a curative treatment) is highly complex not least because this is an incredibly multi-faceted condition (there have been calls by some doctors to officially recognise obesity as a disease). One therapeutic intervention, such as intermittent fasting, on its own, is not going to be sufficient for a lot of people. This certainly is my experience in clinical practice when one has to consider the impact of stress, poor sleep, relevant nutritional/vitamin deficiencies, the state of the “good” bacteria in the gut etc and treat holistically, the individual rather than simply presenting a diet plan.
 
Yours Sincerely,
 
Dr Abbi Lulsegged
Consultant Physician, Endocrinology & Diabetes
BMI and HCA Healthcare
P O Box 885, Bromley, BR1 9EJ
[i] Lai M et al You are what you eat, or are you? The challenges of translating high-fat fed rodents to human obesity and diabetes. Nutrition and Diabetes 2014; 4(9), e135
[ii] Harvie M et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers. A randomised trial in young overweight women. Int J Obes 2011; 35(5): 714-727

Dear Sir,
Thank you for the article, “Fasting diets may raise risk of diabetes, researchers warn” written by Robin McKie and published on 20th May 2018. We wanted to bring to your attention and to your wider readers, several caveats that are necessary in interpreting this work. The work was accepted as a poster/abstract at our recent annual European Congress of Endocrinology meeting. Firstly, the experiment was not performed in humans, but in a type of rat known as Wistar rats. This is an important point because, whereas animal models provide a basis for understanding human physiology and pathology, data obtained from experiments in animal models cannot be automatically extrapolated to humans. Papers have been published encouraging caution particularly in animal models of obesity[i]. Additionally, the rats were fasted for 24 hours every other day – proportionately one wonders if the duration of the fasting period might have been too long. We do not know if this might have been interpreted as a “stressful” event for the rats, moving the intervention from a possible beneficial event to a harmful one. Stress can promote the release of key hormones such as cortisol and ghrelin which promote weight gain and hunger respectively.
 
Secondly, and more importantly, we have intermittent fasting studies performed in humans with excellent outcomes. In one such study of overweight women who fasted two days a week (on the days, they fasted they restricted their calories significantly but did not stop eating), there were significant reductions in insulin levels – a highly desirable finding for preventing diabetes mellitus compared to the group of women who had simply restricted calorie intake[ii]. Crucially, human studies of intermittent fasting in which no calories are consumed – either continuously or intermittently show improved metabolism and weight loss.
 
Thirdly, rather than intermittent fasting promoting diabetes, for reasons partly alluded to above amongst others, this form of diet especially when combined with a reduction in sugars and total carbohydrate intake can work powerfully to control diabetes in the early stages preventing progression if not reversing it in select cases.
 
Ultimately, research into obesity (for the purposes of finding a curative treatment) is highly complex not least because this is an incredibly multi-faceted condition (there have been calls by some doctors to officially recognise obesity as a disease). One therapeutic intervention, such as intermittent fasting, on its own, is not going to be sufficient for a lot of people. This certainly is my experience in clinical practice when one has to consider the impact of stress, poor sleep, relevant nutritional/vitamin deficiencies, the state of the “good” bacteria in the gut etc and treat holistically, the individual rather than simply presenting a diet plan.
 
Yours Sincerely,
 
Dr Abbi Lulsegged
Consultant Physician, Endocrinology & Diabetes
BMI and HCA Healthcare
P O Box 885, Bromley, BR1 9EJ
[i] Lai M et al You are what you eat, or are you? The challenges of translating high-fat fed rodents to human obesity and diabetes. Nutrition and Diabetes 2014; 4(9), e135
[ii] Harvie M et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers. A randomised trial in young overweight women. Int J Obes 2011; 35(5): 714-727

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