Can food type have any effect on weight loss even though net calories would remain constant?

For example, The Fast Diet FAQ, which is a diet based on Intermittent fasting, contains the following question:

What foods should I avoid on a fast day?

It is best to avoid refined carbs on fast days ie anything white or rich in sugar. That means pasta, rice and potatoes, as well as the more obvious things like donuts!

In this example, will these types of food lessen the effect of the diet due to the way energy is released from these foods, or could the reason be to simply remain satiated?

Does the type of foods eaten affect a calorie restricted diet, and is there any evidence for this?

Please leave willpower out of the equation. Assume the person has total control on the foods ingested - I'm just interested in what effect it would have on weight loss.

  • 1
    Can you focus this question to a single claim, for example whether the diet works? Simply asking whether a particular bit of a diet plan "affects" a diet is not a claim we can address.
    – Sklivvz
    Commented Feb 3, 2014 at 12:10
  • I see what you're saying - my question assumes that the diet works and is written on that basis. I believe it does work from what I've read, but I notice you don't have an answer yet to this question. So you'd like me to ask whether it does work first and then ask this question on the back of it? Or I should ask whether the particular mechanism within the diet is disrupted by the type of calorie eaten (regardless of whether the diet itself works)? Commented Feb 3, 2014 at 13:24
  • 1
    "Does the type of calories eaten affect the diet, and is there any evidence for this?". This question could be good if generalized to any diet and and reworded because there are "types of foods" but not "types of calories".
    – Sklivvz
    Commented Feb 3, 2014 at 15:24
  • 1
    Very good edit, reopening!
    – Sklivvz
    Commented Feb 3, 2014 at 19:46

3 Answers 3


The largest prospective study that I am aware of in the EPIC-PANACEA study which has followed over 373,000 men and women over 5 years [1] and recruited subjects between the years 1992 and 2000 in 10 European countries

Our objective was to assess the association between consumption of total meat, red meat, poultry, and processed meat and weight gain after 5 y of follow-up, on average, in the large European population who participated in the European Prospective Investigation into Cancer and Nutrition-Physical Activity, Nutrition, Alcohol, Cessation of Smoking, Eating Out of Home and Obesity (EPIC-PANACEA) project.

This showed that even adjusting for calories, you were more likely to gain weight when eating meat or poultry.

Total meat consumption was positively associated with weight gain in men and women, in normal-weight and overweight subjects, and in smokers and nonsmokers. With adjustment for estimated energy intake, an increase in meat intake of 250 g/d (eg, one steak at approximately 450 kcal) would lead to a 2-kg higher weight gain after 5 y (95% CI: 1.5, 2.7 kg). Positive associations were observed for red meat, poultry, and processed meat.

They then looked to see if fruit and vegetable intakes influenced weight change but there was only a weak association between failure to gain weight in women who gave up smoking.[2]

In this large study, higher baseline fruit and vegetable intakes, while maintaining total energy intakes constant, did not substantially influence midterm weight change overall but could help to reduce risk of weight gain in persons who stop smoking. The interactions observed in women deserve additional attention.

As to why those who consume meat tend to gain weight, whereas those who don't are less likely, it has been shown that the intestinal microbiota differs in omnivores [3]

Vegetarians had a 12% higher abundance of bacterial DNA than omnivores, a tendency for less Clostridium cluster IV (31.86 +/- 17.00%; 36.64 +/- 14.22%) and higher abundance of Bacteroides (23.93 +/- 10.35%; 21.26 +/- 8.05%), which were not significant due to high interindividual variations. PCA suggested a grouping of bacteria and members of Clostridium cluster IV. Two bands appeared significantly more frequently in omnivores than in vegetarians (p < 0.005 and p < 0.022). One was identified as Faecalibacterium sp. and the other was 97.9% similar to the uncultured gut bacteriumDQ793301.

One current thought is that the bacteria in the gut of a human omnivore is more able to metabolise food releasing nutrients otherwise unavailable to vegetarians. This might account for about 2% of the daily food intake, and works out to be about 5 lbs of weight gain a year.

[1] Vergnaud AC, Norat T, Romaguera D, Mouw T, May AM, Travier N, Luan J, Wareham N, Slimani N, Rinaldi S, Couto E, Clavel-Chapelon F, Boutron-Ruault MC, Cottet V, Palli D, Agnoli C, Panico S, Tumino R, Vineis P, Agudo A, Rodriguez L, Sanchez MJ, Amiano P, Barricarte A, Huerta JM, Key TJ, Spencer EA, Bueno-de-Mesquita B, Büchner FL, Orfanos P, Naska A, Trichopoulou A, Rohrmann S, Hermann S, Boeing H, Buijsse B, Johansson I, Hellstrom V, Manjer J, Wirfält E, Jakobsen MU, Overvad K, Tjonneland A, Halkjaer J, Lund E, Braaten T, Engeset D, Odysseos A, Riboli E, Peeters PH. Meat consumption and prospective weight change in participants of the EPIC-PANACEA study. Am. J. Clin. Nutr. 2010 Aug;92(2):398-407. doi: 10.3945/ajcn.2009.28713. PubMed PMID: 20592131.

[2] Vergnaud AC, Norat T, Romaguera D, Mouw T, May AM, Romieu I, Freisling H, Slimani N, Boutron-Ruault MC, Clavel-Chapelon F, Morois S, Kaaks R, Teucher B, Boeing H, Buijsse B, Tjønneland A, Halkjaer J, Overvad K, Jakobsen MU, Rodríguez L, Agudo A, Sánchez MJ, Amiano P, Huerta JM, Gurrea AB, Wareham N, Khaw KT, Crowe F, Orfanos P, Naska A, Trichopoulou A, Masala G, Pala V, Tumino R, Sacerdote C, Mattiello A, Bueno-de-Mesquita HB, van Duijnhoven FJ, Drake I, Wirfält E, Johansson I, Hallmans G, Engeset D, Braaten T, Parr CL, Odysseos A, Riboli E, Peeters PH. Fruit and vegetable consumption and prospective weight change in participants of the European Prospective Investigation into Cancer and Nutrition-Physical Activity, Nutrition, Alcohol, Cessation of Smoking, Eating Out of Home, and Obesity study. Am. J. Clin. Nutr. 2012 Jan;95(1):184-93. doi: 10.3945/ajcn.111.019968. PubMed PMID: 22170373.

[3] Liszt K, Zwielehner J, Handschur M, Hippe B, Thaler R, Haslberger AG. Characterization of bacteria, clostridia and Bacteroides in faeces of vegetarians using qPCR and PCR-DGGE fingerprinting. Ann. Nutr. Metab. 2009 Jul 27;54(4):253-7. doi: 10.1159/000229505. PubMed PMID: 19641302.

  • Huh. So it sounds like the issue is that eating meat means your body is getting more nourishment than on a vegetation-only diet. That makes sense. Commented Jun 5, 2014 at 12:25
  • Yes, and in this era, it's more unnecessary nutrition.
    – HappySpoon
    Commented Jun 5, 2014 at 20:54
  • "With adjustment for estimated energy intake..." To me, it sounds unlikely they knew the exact calorie intake in free-living study participants over the 5 years; they probably only interviewed them what they eat and not actually measured their calorie intake. Also, their conclusion says "Positive associations were observed for red meat, poultry, and processed meat." "Association" is not already a cause-effect relationship.
    – Jan
    Commented Oct 17, 2014 at 9:09

Can food type have any effect on weight loss even though net calories would remain constant?

Surely it can in many ways.

Calories and absorption are very different things. You eat x calories, but your gut absorbs y% of that. As HappySpoon already mentioned the absorption rate depends on the gut flora as well.

The fibre content of the food can speed up your gut motion and probably decrease the y, while meat poor in dietary fiber can slow down your gut motion and increase the y.

The fibre content and sweeteners can change the gut flora.

Your low kcal diet can change the gut flora as well.

These results show that the nutrient load is a key variable that can influence the gut (fecal) bacterial community structure over short time scales. Furthermore, the observed associations between gut microbes and nutrient absorption indicate a possible role of the human gut microbiota in the regulation of the nutrient harvest.

So your preferred food can change your gut flora and so the absorption too. Your gut can possibly absorb more or less calories...

If your food does not contain enough minerals, like zinc, or your gut flora causes an inflammation which prevents the absorption of zinc, then you will have zinc deficiency, and so your leptin level will elevate. After that you will develop a leptin resistance, so you will be always hungry, and it will be much harder to stick to your diet. The same thing happens if you develop an insuline resistance somehow possibly with fast sugars. Note that this is just a very small part of the story, human physiology is a very complicated thing...

The Western diet, comprised of highly refined carbohydrates and fat but reduced complex plant polysaccharides, has been attributed to the prevalence of obesity. A concomitant rise in the consumption of fructose and sugar substitutes such as sugar alcohols, artificial sweeteners, even rare sugars, has mirrored this trend, as both probable contributor and solution to the epidemic. Acknowledgement of the gut microbiota as a factor involved in obesity has sparked much controversy as to the cause and consequence of this relationship. Dietary intakes are a known modulator of gut microbial phylogeny and metabolic activity, frequently exploited to stimulate beneficial bacteria, promoting health benefits. Comparably little research exists on the impact of ‘unconscious’ dietary modulation on the resident commensal community mediated by increased fructose and sugar substitute consumption. This review highlights mechanisms of potential host and gut microbial fructose and sugar substitute metabolism. Evidence is presented suggesting these sugar compounds, particularly fructose, condition the microbiota, resulting in acquisition of a westernized microbiome with altered metabolic capacity. Disturbances in host–microbe interactions resulting from fructose consumption are also explored.

Zinc (Zn) deficiency and obesity are global public health problems. Zn deficiency is associated with obesity and comorbid conditions that include insulin resistance and type 2 diabetes. However, the function of Zn in obesity remains unclear.

Our results demonstrate that Zn deficiency increases leptin production and exacerbates macrophage infiltration into adipose tissue in obese mice, indicating the importance of Zn in metabolic and immune dysregulation in obesity.

In obesity, anorectic responses to leptin are diminished, giving rise to the concept of “leptin resistance.” Increased expression of protein tyrosine phosphatase 1B (PTP1B) has been associated with the attenuation of leptin signaling and development of cellular leptin resistance.


Calories are calories, and carbohydrates, in general, have very high satiety ratings (albeit possibly less than protein). However, refined carbohydrates are an exception. Their lack of fiber and other "bulk" gives them a high glycemic index. Your body processes them and burns the energy quickly, leaving you wanting more. Thus, refined carbohydrates are more likely to leave you feeling hungry and thus more likely to have "just one more" in your snacking. As to whether bread and pasta are simple or complex carbohydrates, that's more controversial. Most breads and pasta, even ones made using refined grains, contain relatively little sugar and have sufficient bulk to slow the uptake of the energy. To use a simple (possibly oversimplified) analogy, simple carbohydrates are like trying to fuel a fire with kerosene. It burns too quickly to sustain.

I would also suggest avoiding salty and/or fried food. As with sugar, it packs a lot of caloric energy in a small package that's absorbed quickly. In addition, it hits a number of tastebud areas that can result in overeating of them. Potato chips, in particular, hit that sweet spot where many people do very badly at only eating a small quantity.

  • A number of your claims are unreferenced - including the entire last paragraph. "Calories are calories" begs the question.
    – Oddthinking
    Commented Jun 3, 2014 at 12:41
  • are more likely to leave you feeling hungry - apart from feeling hungry (say you had enough willpower to avoid acting on this), would it affect the diet? Commented Jun 3, 2014 at 15:07
  • My understanding is, the answer there is no. Scientific study of diets repeatedly shows that what matters is calories in and calories out. The type of food is a matter of nutrition. Weight loss and weight gain is a matter of calories. That said, regarding willpower, there are a large number of studies showing that low glucose, or glucose spikes and crashes, have a measurable effect on said willpower even among those people who score high for willpower. Commented Jun 3, 2014 at 15:13
  • @SeanDuggan: Check out Intermittent fasting as an alternative approach (to calorie restriction). Does this throw doubt on calories in vs calories out? Commented Jun 3, 2014 at 15:46
  • Huh. In lab rats, IF seems to decrease the effects of reduced caloric intake such that the IF rats were gaining weight on a reduced amount of food. In his paper, Dr. Mattsen theorizes that it may be due to mouse gorging behavior. He then completely dismisses it as inapplicable to humans while he proceeds to state that all of the other findings in mice are applicable to humans. That seems like bad science to me. Commented Jun 3, 2014 at 16:00

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