Which is Better at Reducing Abdominal Obesity: Low Carb or IF?
You might be surprised by the results of this randomized trial published in Cell Reports.
I sometimes find that low-carb people aren’t always fans of intermittent fasting, and some intermittent fasters are down on low-carb. I like to consider all approaches.
The journal Cell Reports published this randomized trial comparing three different approaches: low-carb, intermittent fasting, and a combination of both.
The researchers were especially interested in reducing abdominal obesity rather than only total body fat. This is because abdominal obesity strongly correlates with heart disease, diabetes, and other metabolic disorders.
The authors note in their introduction:
Abdominal obesity is of central importance in the induction of metabolic dysfunctions including hypertension [high blood pressure], hyperglycemia [high blood sugar], atherogenic dyslipidemia [narrowing of arteries], and release of proinflammatory cytokines by adipose tissue. 1
The researchers recruited 169 participants with metabolic syndrome and randomized them into three interventions: a low carb diet (LCD) group, a time-restricted eating group (TRE), and a group that did both interventions. The trial lasted for three months.
Those practicing intermittent fasting or TRE [time restricted eating] had 8-hour eating windows. They could choose between an early eating window of 8 am to 4 pm, or an evening eating window of 12 pm to 8 pm. It’s interesting to me that more people chose the early eating window.
Results: TRE alone is better than Low-carb alone
Researchers found that:
As compared with baseline, all three treatments induced a significant reduction of waist circumference, hip circumference, and body fat mass after 3 months of intervention. Nevertheless, only TRE induced a more prominent reduction of WHR [waist hip ratio] compared with LCD and combination, suggesting that TRE more effectively alleviates abdominal obesity than LCD.2
Here’s a graph the researchers made to summarize their findings:
The first row shows that for total body weight, the low carb group lost a little, the TRE non low-carb group lost more weight, and the group who did both lost the most.
The second row shows that all three strategies worked for reducing subcutaneous fat, or the fat under our skin.
However, the third row shows that those practicing TRE without low carb lost more of the visceral fat, or the fat around their internal organs, than those who did low carb but didn’t fast. As would be expected, the combination group lost the most visceral fat.
Since abdominal fat is related to high insulin, it makes sense that fasting is necessary to eliminate that fat. Although eating low carb will cause insulin to go down a little, some insulin is still released whenever we eat, even if we avoid carbs. This is why refraining from food altogether for long periods is the best way to drop basal insulin and visceral fat.
The final row shows that low carb was less effective than TRE alone or the combo at giving glycemic control (a measure of how sensitive our cells are to insulin), regulating dyslipidemia (triglycerides in blood), and reducing uric acid.
Some additional interesting takeaways:
TRE without low carb was much better than low carb alone at reducing triglycerides:
LCD did not cause any significant differences in plasma levels of TG [triglycerides], HDL-c, or the ratio between TG and HDL-c (TG/HDL-c ratio) after 3 months of intervention (Figures 3F, 3G, and 3H and Table 2). In marked contrast, TRE with and without LCD significantly reduced TG level and TG/HDL-c ratio, and the change in TG and TG/HDL-c ratio was significantly different between LCD and combination treatment.
Details are important here! I have often said that many cardiologists no longer believe that LDL cholesterol, the supposed bad form of cholesterol causes heart disease. I stand by that. However, triglycerides are a different story. Cardiologists coming from all perspectives agree that everyone should have a low triglyceride to HDL ratio.
Let’s say your triglycerides are 150 and your HDL is 75. That’s a 2 to 1 ratio and is considered too high. It’s optimal to have your triglycerides as close to HDL as you can making a 1:1 ratio, such as triglycerides at 75 and HDL at 75. This is a profound marker of good health. It’s interesting to me that low carb alone didn’t improve this ratio but TRE apart from low carb did. Triglycerides usually trend high in diets packed with sugar and carbs. However, it appears that the time spent fasting compensates for eating carbs.
Fasting Reduces Blood Pressure
Finally, researchers found that:
TRE with and without LCD, but not LCD alone, reduces diastolic blood pressure.
The researchers particularly noted that higher blood pressure correlates with higher visceral fat, so it’s likely that as the fasting reduced abdominal fat, this, in turn, helped to lower blood pressure.
My Personal Take-Away: If you’re already eating a low-carb lifestyle, you can multiply your efforts by adding in some intermittent fasting. If you’re already practicing IF, reducing your carbs a bit will give you even better results.
Fast on Friends,
Leslie Dennis Taylor
If you’re new around here, you may enjoy reading about:
A Harvard Professor who is curing mental illness through diet
Some success stories of people who have reversed their diabetes
How fasting can upgrade your brain
Why you need to quit seed oils yesterday
Why everyone should get off statins and never go back
https://doi.org/10.1016/j.xcrm.2022.100777
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Heard your interview with gin stevens... one of the podcast I always listen too, so I wanted to read your stuff. I have been IF since 2019, and I love knowing about it... I am going to be 71 and I wish I could have found it sooner! I did the juice fasting with joe cross... over that!!! Found dr. Jason Fung and have not looked back... these are my people... like you. Thanks for all you do!!!
Fascinating. I have been doing IF for 8 months. Have lost 30 lbs --so far. My husband just had double bypass surgery for totally blocked arteries, that was never caught! LDL was always in a good range, as was total cholesterol. However, his triglycerides/HDL ratio was horrible. Easing him into TRE--struggling to know how quickly to move into this with the major healing he is doing. This articles is awesome. My second phase was to clean up what we eat, and reduce carbs (not full Keto), and move more. This makes me feel much more confident in our journey.