Are Low Carb Diets Better for Appetite Suppression? New Study Disputes Keto Mantra

How to eat for weight loss (and overall health) is one of the most confusing topics for the average person.

And, it’s easy to understand why dieting is so confusion especially when you consider the laundry list of tricksters, charlatans, and “gurus” pushing their own money-making diet as “the secret” to effortless fat loss and better health and wellness.

In recent times, high-fat, low carb diets have been all the rage, thanks in large part to the explosion of keto, Primal, and Carnivore diets.

Yet, for the longest time dietary fat was the most controversial macronutrient, and consuming too much of it was a certified first-class ticket to a coronary.

This constant back and forth has left the average Joe and Jane floundering in a sea of confusion, misdirection, and bad information when all they really need is someone who doesn’t stand to gain from their ignorance to lend a helping hand.

So, for the average individual looking to shed some unwanted body fat and improve their health and wellness, what is the best diet?

As much as you’d like for me to give you a straightforward answer, the truth is, there is no single “best” fat loss diet for every single person all the time.

There are certain immutable truths when it comes to dieting and fat loss (i.e. you need to be in an energy deficit to lose weight), but as far as how that reduced-calorie diet is constructed is highly individualistic.

Most “diets” do work in the beginning, but they fail long-term due to the fact that the diets aren’t sustainable as they leave individuals feeling incessantly hungry and/or the diet is too tedious to maintain day-to-day.

Previous studies have shown that ketogenic or very-low carbohydrate diets (carb <10% daily energy intake) where individuals were allowed to consume protein and fat ad libitum reduced subjective ratings of hunger and desire to eat as well as increased fullness/satiety to a greater extent than higher carbohydrate diets.[2,3,4]

Based on this small body of evidence, keto, carnivore, and Primal lifestyle acolytes champion the low-carb/no-carb diet as the be-all, end-all way to eat to kill hunger, burn fat, and get ripped.

But, a new study disputes these results and finds that a higher carbohydrate, lower fat diet may actually help reduce appetite more.[1]

The Study

The study titled, Very Low and Higher Carbohydrate Diets Promote Differential Appetite Responses in Adults with Type 2 Diabetes: A Randomized Trial, sought to compare the effects of a very-low carb diet vs a high-carb diet on self-reported measures of appetite at baseline and after 4 and 16 weeks in overweight or obese type 2 diabetics.[1]

The study included 115 adults (aged 35–68 years old) who were overweight or obese with type 2 diabetes.

Subjects were randomized into one of two energy-restricted (500-1000 calories per day) diets:

• Very-Low Carb Diet: 14% carbohydrate (<50 g/d), 28% protein, 58% fat (<10% of total energy intake from saturated fat)
• High Carb Diet: 53% carbohydrate, 17% protein, 30% fat (<10% of total energy intake from saturated fat)

Subjects followed this diet recommendation for 2 years.

During the first 3 months (12 weeks) of the study, researchers provided subjects with 30% of the “key foods” representative of each person’s assigned diet to help them hit their macronutrient targets.

After the initial 12 weeks, participants were given with “key food packs” along with a 50-dollar voucher to subsidize the purchase of these “key foods” every other month. 

During the study, participants prepared and purchased their own meals according to guidelines outlined by the research staff.

Furthermore, subjects all participated in the same professionally-supervised 3-day workout program which consisted of 60-min exercise classes containing a mix of moderate-intensity cardio and resistance exercise.

Results

After 16 weeks, researchers found that:

"The primary findings of this study showed that prescriptive energy-restricted, isocaloric HC and VLC diets promoted comparable effects on fasting perceptions of appetite in overweight/obese individuals with type 2 diabetes. However, the HC diet resulted in greater “daily overall” fullness and reduced prospective consumption. Despite these observed differences, body weight changes were similar in both groups."[1]

“In summary, a prescribed energy-reduced HC diet promoted greater perceptions of fullness and reduced perceptions of prospective consumption over the day compared to an energy-matched VLC diet in individuals who were overweight or obese with type 2 diabetes.”[1]

The interesting thing (and the thing that Keto zealots always hit on) is that fat is "more filling" and leads to less cravings than high carb diets that are lower in fat.

As the researchers point out, a previously conducted "meta analysis" (which included all of 3 studies, fyi) found that higher fat, lower carb diets more effectively suppressed hunger and cravings than higher carb, lower fat diets.[5]

Discussion

The present study shows that a high-carb diet can feel more filling and leave dieters with less feelings of hunger than a high fat diet.

Interestingly, while previous studies found that higher fat diets are better for keeping hunger at bay while dieting, when you start to dig further into the aforementioned studies showing low-carb/keto diets suppress hunger to a greater extent than high-carb diets, you’ll find the appetite-suppressing effects of high fat diets don’t last forever.

For example, Martin et al.[4] found that an ad libitum very-low carb diet (<20 g carbohydrates per day) reduced hunger ratings compared to a low-calorie high-carb diet (55% calories from carbohydrate after 12 weeks.[4]

However, after 6 months and 24 months, there were no differences in hunger ratings between the low carb and high carb diets.[4]

In other words, low-carb diets may help to reduce feelings of hunger or fullness more than higher-carb diets in the early days and weeks of a diet, but those effects subside with time.

The present RCT continues to drive home the point that there is no one diet that is "perfect" for everyone...some individuals experience higher satiety following a higher carb, lower fat diet while others experience higher satiety and less hunger going low carb and high fat.

One of the reasons that the higher carb diet may have led to greater satiety (even though both groups had roughly the same amount of calories removed from the diet) is that the individuals consuming more carbs consumed greater total volume of food daily (~1430g for the high-carb diet compared to ∼970g for the low-carb diet).[6]

This makes sense that the higher carb diet would consume a greater volume of food compared to the high-fat, very-low carb dieters since fat is more energy dense than carbohydrates.

FYI, fat contains 9 calories per gram and carbohydrate contains 4 calories per gram.

What this means is that if two people are eating the same amount of calories, but one eats high carb and one eats low carb, the high-carb dieter eats a greater volume of food for the same amount of calories compared to the high-fat dieter.

We also know that higher-volume foods tend to reduce hunger and perceived feelings of appetite, too.[7]

This may explain why the high-carb group experienced greater fullness during the day along with a lower desire to eat -- the got to eat more food.

One thing that would be interesting to see is what would happen if both diets had a higher contribution of protein, to the tune of 1 gram per pound.

We know that protein is the most satiating macronutrient (meaning it helps keep you feeling full), and the most metabolically expensive for the body to digest.

Would these differences be even greater if protein was equated between the groups, or would the differences be eliminated?

Personally, I’m still wondering why so many nutrition trials continue to “underdose” protein intake when one of the metrics they’re gathering is weight loss. But, that’s a topic for another article.

Takeaway

Both higher carb, low-fat diets and low carb, high fat diets can work for weight loss, and this has been shown time and time again in research.[8,9,10,11,12]

So long as calories and protein intake are controlled for, it really doesn’t matter which diet an individual follows.

It’s worth noting that both groups experienced similar reductions in body weight (again driving home the fact that calories are king for weight loss).

Individuals following the very-low carb diet experienced greater reductions in blood glucose-lowering medication and greater improvements in glycemic and blood lipid profile. This makes sense given the fact that the very-low carb group consumed very little carbohydrates, which directly impact insulin secretion (and the need for it).

In closing, both high-carb and low-carb diets can work for weight loss, and the “belief” propagated by low-carb zealots that high-fat diets are more satiating isn’t entirely true.

High-fat diets can be more satiating for some dieters, but others fare better on a higher-carb, lower fat diet.

Lastly, this study was performed in overweight diabetics -- individuals who are known to have impaired hunger and satiety hormone function (ghrelin, leptin, and glucagon-like peptide 1). So if a high-carb, reduced-calorie diet can help those individuals feel fuller and experience weight loss, imagine what it can do for individuals with normal hormone function.

What do you think about the study and which diet is best for killing hunger on a cut?

References

1. Noor A Struik, Grant D Brinkworth, Campbell H Thompson, Jonathan D Buckley, Gary Wittert, Natalie D Luscombe-Marsh, Very Low and Higher Carbohydrate Diets Promote Differential Appetite Responses in Adults with Type 2 Diabetes: A Randomized Trial, The Journal of Nutrition, , nxz344, https://doi.org/10.1093/jn/nxz344
2. Johnstone  AM, Horgan GW, Murison  SD, Bremner DM, Lobley GE. Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum. Am J Clin Nutr. 2008;87:44–55.
3. Ratliff  J, Mutungi  G, Puglisi MJ, Volek  JS, Fernandez ML. Carbohydrate restriction (with or without additional dietary cholesterol provided by eggs) reduces insulin resistance and plasma leptin without modifying appetite hormones in adult men. Nutr Res. 2009;29:262–8.
4. Martin  CK, Rosenbaum  D, Han H, Geiselman  PJ, Wyatt HR, Hill JO, Brill  C, Bailer B, MillerBV III, Stein  R et al. . Change in food cravings, food preferences, and appetite during a low-carbohydrate and low-fat diet. Obesity. 2011;19:1963–70.
5. Gibson  AA, Seimon R  V, Lee CMY, Ayre  J, Franklin J, Markovic  TP, Caterson ID, Sainsbury  A. Do ketogenic diets really suppress appetite? A systematic review and meta-analysis. Obes Rev. 2015;16:64–76.
6. Tay J, Luscombe-Marsh ND, Thompson CH, Noakes M, Buckley JD, Wittert GA, Yancy WS, Brinkworth GD. Comparison of low- and high- carbohydrate diets for type 2 diabetes management: a randomized trial. Am J Clin Nutr 2015;102:780–90.[6]
7. Latner, J. D., Rosewall, J. K., & Chisholm, A. M. (2009). Food volume effects on intake and appetite in women with binge-eating disorder and weight-matched controls. The International Journal of Eating Disorders, 42(1), 68–75. https://doi.org/10.1002/eat.20570
8. Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial [published correction appears in JAMA. 2018 Apr 3;319(13):1386] [published correction appears in JAMA. 2018 Apr 24;319(16):1728]. JAMA. 2018;319(7):667–679. doi:10.1001/jama.2018.0245
9. Cynthia A. Thomson, Alison T. Stopeck, Jennifer W. Bea, Ellen Cussler, Emily Nardi, Georgette Frey & Patricia A. Thompson (2010)Changes in Body Weight and Metabolic Indexes in Overweight Breast Cancer Survivors Enrolled in a Randomized Trial of Low-Fat vs. Reduced Carbohydrate Diets, Nutrition and Cancer, 62:8, 1142-1152, DOI: 10.1080/01635581.2010.513803
10. Carol S Johnston, Sherrie L Tjonn, Pamela D Swan, Andrea White, Heather Hutchins, Barry Sears, Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets, The American Journal of Clinical Nutrition, Volume 83, Issue 5, May 2006, Pages 1055–1061, https://doi.org/10.1093/ajcn/83.5.1055
11. Phillips SA, Jurva JW, Syed AQ, et al. Benefit of low-fat over low-carbohydrate diet on endothelial health in obesity. Hypertension. 2008;51(2):376–382. doi:10.1161/HYPERTENSIONAHA.107.101824
12. Hu T, Mills KT, Yao L, et al. Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors: a meta-analysis of randomized controlled clinical trials. Am J Epidemiol. 2012;176 Suppl 7(Suppl 7):S44–S54. doi:10.1093/aje/kws264
13. Malinska H, Kahleova H, Topolcan O, Vrzalova J, Oliyarnyk O, Kazdova L, Belinova L, Hill M, Pelikanova T. Postprandial oxidative stress and gastrointestinal hormones: is there a link? Andrews Z, editor. PLoS One 2014;9:e103565.
14. Enriori PJ, Evans AE, Sinnayah P, Jobst EE, Tonelli-Lemos L, Billes SK, Glavas MM, Grayson BE, Perello M, Nillni EA, et al. Diet- induced obesity causes severe but reversible leptin resistance in arcuate melanocortin neurons. Cell Metab 2007;5:181–94.
15. Verdich C, Toubro S, Buemann B, Lysgård Madsen J, Juul Holst J, Astrup A. The role of postprandial releases of insulin and incretin hormones in meal-induced satiety-effect of obesity and weight reduction. Int J Obes 2001;25:1206–14.