The question has been a long unsettled question of debate between the Low Carb and Low Fat diet adherents. Here’s a good article which provides some insight from world population data (The Rise of Obesity and How to Make It Stop).
As for keto, here’s a good article on Seven Common Keto Diet Myths. I agree with every one of these being a myth which sidetracks keto dieters.
One of the things that keto folks sometimes notice is an increase in blood lipids on the keto diet. This may be in some part due to increased coffee consumption. I never used to drink coffee but I started drinking coffee on keto for extra energy.
The association between boiled and filter coffee consumption and levels of cholesterol, triglycerides and blood pressure was studied, including 14168 men and 14859 women. A total of 94% drank coffee, 55% of the men and 48% of the women drank more than 4 cups per day. The type of coffee consumed varied between the counties, from 11 to 49% boiled and 49 to 87% filter coffee. Serum cholesterol increased linearly with increasing coffee consumption, and most strongly for boiled coffee. Controlling for other variables gave, for boiled coffee, an 8% increase for men and 10% for women. For filter coffee drinkers the coffee dose-cholesterol association remained significant only for women. Triglycerides showed a negative association with coffee, significant after adjustment for other variables. This effect was stronger for filter than for boiled coffee in both sexes. For men and women drinking 1 cup of coffee or more, a significant negative association between both systolic and diastolic blood pressure and number of cups of filter coffee was found.
Not going to change my life but perhaps a talking point with my doctor if my numbers are high.
One of the slides really ties things together for me. There’s a debate in the keto community over which macronutrient provides the most satiety. We all agree it is not carbohydrates. Some of us say it’s fat which most satisfies our hunger. Others say it’s protein. I tend towards the protein side of the question but have found it to still be an open issue.
Role of Hormones – Ghrelin and Leptin
The hunger hormone Ghrelin is the key to refeeding. Roughly speaking, if your Ghrelin goes below a baseline you are less hungry. If it goes above the baseline you are more hungry.
Leptin is a mediator of long-term regulation of energy balance, suppressing food intake and thereby inducing weight loss. Ghrelin on the other hand is a fast-acting hormone, seemingly playing a role in meal initiation.
Let’s look at each of the three macronutrients and their effect on hunger via their impact on Ghrelin levels.
Carbohydrates provided the greatest drop in Ghrelin for the first 140 minutes. They also have a significantly bigger Area Under the Curve (AUC) during that period. After that the slope rises dramatically. By 240 minutes the graph shows Ghrelin crossing over the baseline and going above the baseline. The slope up is shown roughly in the red line below.
That’s why you feel hunger when you eat carbohydrates and why you want to eat again just a couple of hours later. For me this comes to mind:
It’s the slope of the line up that drives you to want to refeed.
They keto community is correct. Fat (lipid) does drop Ghrelin. It does a decent job since it stays below baseline for many hours. Here’s the rough area under the curve (AUC) for Ghrelin after eating fat during those hours.
This explains to me why some people feel that Bulletproof Coffee works for them. It helps them not be hungry for hours. Fat alone help you stay below baseline levels of Ghrelin.
Here’s where the paper answers the question asked in the opening paragraphs of this page. Which macronutrient provides the best depression of Ghrelin? Clearly protein wins the battle. Here’s the AUC for protein:
Protein vs Fat
Putting both Protein and Fat AUCs together something interesting becomes clear.
There’s nothing that fat does that protein doesn’t do even better for depressing Ghrelin levels. Particularly at several hours in. They both keep the Ghrelin levels below baseline but protein does it longer and deeper. Yes, you do get hungry again when you return to near baseline at 6 hours in.
The debate will continue in the keto community until people actually examine the science. It seems pretty clear that protein is a superior choice to fat when taken in isolation. Both together seem like a fine choice so on some level both sides are correct.