Dietary fiber intake provides many health benefits. However, average fiber intakes for US children and adults are less than half of the recommended levels. Individuals with high intakes of dietary fiber appear to be at significantly lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases. Increasing fiber intake lowers blood pressure and serum cholesterol levels. Increased intake of soluble fiber improves glycemia and insulin sensitivity in non-diabetic and diabetic individuals. Fiber supplementation in obese individuals significantly enhances weight loss. Increased fiber intake benefits a number of gastrointestinal disorders including the following: gastroesophageal reflux disease, duodenal ulcer, diverticulitis, constipation, and hemorrhoids. Prebiotic fibers appear to enhance immune function. Dietary fiber intake provides similar benefits for children as for adults. The recommended dietary fiber intakes for children and adults are 14 g/1000 kcal. More effective communication and consumer education is required to enhance fiber consumption from foods or supplements.

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Health benefits of dietary fiber

Relationship between stress, eating behavior, and obesity.

Acute inflammation is a response to an alteration induced by a pathogen or a physical or chemical insult, which functions to eliminate the source of the damage and restore homeostasis to the affected tissue. However, chronic inflammation triggers cellular events that can promote malignant transformation of cells and carcinogenesis. Several inflammatory mediators, such as TNF-α, IL-6, TGF-β, and IL-10, have been shown to participate in both the initiation and progression of cancer. In this review, we explore the role of these cytokines in important events of carcinogenesis, such as their capacity to generate reactive oxygen and nitrogen species, their potential mutagenic effect, and their involvement in mechanisms for epithelial mesenchymal transition, angiogenesis, and metastasis. Finally, we will provide an in-depth analysis of the participation of these cytokines in two types of cancer attributable to chronic inflammatory disease: colitis-associated colorectal cancer and cholangiocarcinoma.

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Chronic inflammation and cytokines in the tumor microenvironment.

The effects of adrenal corticosteroids on subsequent adrenocorticotropin secretion are complex. Acutely (within hours), glucocorticoids (GCs) directly inhibit further activity in the hypothalamo–pituitary–adrenal axis, but the chronic actions (across days) of these steroids on brain are directly excitatory. Chronically high concentrations of GCs act in three ways that are functionally congruent. (i) GCs increase the expression of corticotropin-releasing factor (CRF) mRNA in the central nucleus of the amygdala, a critical node in the emotional brain. CRF enables recruitment of a chronic stress-response network. (ii) GCs increase the salience of pleasurable or compulsive activities (ingesting sucrose, fat, and drugs, or wheel-running). This motivates ingestion of “comfort food.” (iii) GCs act systemically to increase abdominal fat depots. This allows an increased signal of abdominal energy stores to inhibit catecholamines in the brainstem and CRF expression in hypothalamic neurons regulating adrenocorticotropin. Chronic stress, together with high GC concentrations, usually decreases body weight gain in rats; by contrast, in stressed or depressed humans chronic stress induces either increased comfort food intake and body weight gain or decreased intake and body weight loss. Comfort food ingestion that produces abdominal obesity, decreases CRF mRNA in the hypothalamus of rats. Depressed people who overeat have decreased cerebrospinal CRF, catecholamine concentrations, and hypothalamo–pituitary–adrenal activity. We propose that people eat comfort food in an attempt to reduce the activity in the chronic stress-response network with its attendant anxiety. These mechanisms, determined in rats, may explain some of the epidemic of obesity occurring in our society.

https://www.pnas.org/content/pnas/100/20/11696.full.pdf

Chronic stress and obesity: A new view of “comfort food”

Objectives To undertake a systematic review of the long-term effects of obesity treatments on body weight, risk factors for disease, and disease. Methods The study encompassed three systematic reviews that examined different aspects of obesity treatments. (1) A systematic review of obesity treatments in adults where the methods of the Cochrane Collaboration were applied and randomised controlled trials (RCTs) with a follow-up of at least 1 year were evaluated. (2) A systematic epidemiological review, where studies were sought on long-term effects of weight loss on morbidity and/or mortality, and examined through epidemiological modelling. (3) A systematic economic review that sought reports with both costs and outcomes of treatment, including recent reports that assessed the cost-effectiveness of pharmaceutical and surgical interventions. A Markov model was also adopted to examine the cost-effectiveness of a low-fat diet and exercise intervention in adults with obesity and impaired glucose tolerance. Results The addition of the drugs orlistat or sibutramine was associated with weight loss and generally improved risk factors, apart from diastolic blood pressure for sibutramine. Metformin was associated with decreased mortality after 10 years in obese people with type 2 diabetes. Low-fat diets were associated with continuing weight loss for 3 years and improvements in risk factors, as well as prevention of type 2 diabetes and improved control of hypertension. Insufficient evidence was available to demonstrate the benefits of low calorie or very low calorie diets. The addition of an exercise or behaviour programme to diet was associated with improved weight loss and risk factors for at least 1 year. Studies combining low-fat diets, exercise and behaviour therapy suggested improved hypertension and cardiovascular disease. Family therapy was associated with improved weight loss for 2 years compared to individual therapy. There was insufficient evidence to conclude that individual therapy was more beneficial than group therapy. Weight lost more quickly (within 1 year), from the epidemiology review, may be more beneficial with respect to the risk of mortality. The effects of intentional weight loss need further investigation. Weight loss from surgical and non-surgical interventions for people suffering from obesity was associated with decreased risk of development of diabetes, and a reduction in low-density lipoprotein cholesterol, total cholesterol and blood pressure, in the long term. Targeting high-risk individuals with drugs or surgery was likely to result in a cost per additional life-year or quality-adjusted life-year (QALY) of no more than 13,000 British pounds. There was also suggestive evidence of cost saving from treatment of people with type 2 diabetes with metformin. Targeting surgery on people with severe obesity and impaired glucose tolerance was likely to be more cost-effective at 2329 British pounds per additional life-year. Economic modelling over 6 years for diet and exercise for people with impaired glucose tolerance was associated with a high initial cost per additional QALY, but by the sixth year the cost per QALY was 13,389 British pounds. Results did not include cost savings from diseases other than diabetes, and therefore may be conservative. Conclusions The drugs orlistat and sibutramine appear beneficial for the treatment of adults with obesity, and metformin for obese patients with type 2 diabetes. Exercise and/or behaviour therapy appear to improve weight loss when added to diet. Low-fat diets with exercise, or with exercise and behaviour therapy are associated with the prevention of type 2 diabetes and hypertension. Long-term weight loss in epidemiological studies was associated with reduced risk of type 2 diabetes, and may be beneficial for cardiovascular disease. Low-fat diets and exercise interventions in individuals at risk of obesity-related illness are of comparable cost to drug treatments. Long-term pragmatic RCTs of obesity treatments in populations with obesity-related illness or at high risk of developing such illness are needed (to include an evaluation of risk factors, morbidity, quality of life and economic evaluations). Drug trials that include dietary advice, plus exercise and/or behaviour therapy are also needed. Research exploring effective types of exercise, diet or behaviour and also interventions to prevent obesity in adults is required.

Systematic review of the long-term effects and economic consequences of treatments for obesity and implications for health improvement

ContextInvestigators first described the night-eating syndrome (NES), which
consists of morning anorexia, evening hyperphagia, and insomnia, in 1955,
but, to our knowledge, this syndrome has never been subjected to careful clinical
study.ObjectiveTo characterize NES on the basis of behavioral characteristics and neuroendocrine
data.Design and SettingA behavioral observational study was conducted between January 1996
and June 1997 in a weight and eating disorders program at the University of
Pennsylvania. A neuroendocrine study was conducted from May through August
1997 at the Clinical Research Center of the University Hospital, Tromso,
Norway.SubjectsThe behavioral study included 10 obese subjects who met criteria for
NES and 10 matched control subjects. The neuroendocrine study included 12
night eaters and 21 control subjects. Behavioral study subjects were observed
for 1 week on an outpatient basis, and neuroendocrine study subjects were
observed during a 24-hour period in the hospital.Main Outcome MeasuresThe behavioral study measured timing of energy intake, mood level, and
sleep disturbances. The neuroendocrine study measured circadian levels of
plasma melatonin, leptin, and cortisol.ResultsIn the behavioral study, compared with control subjects, night eaters
had more eating episodes in the 24 hours (mean [SD], 9.3 [0.6] vs 4.2 [0.2]; P<.001) and consumed significantly more of their daily
energy intake at night than did control subjects (56% vs 15%; P<.001). They averaged 3.6 (0.9) awakenings per night compared with
0.3 (0.3) by controls (P<.001). In night eaters,
52% of these awakenings were associated with food intake, with a mean intake
per ingestion of 1134 (1197) kJ. None of the controls ate during their awakenings.
In the neuroendocrine study, compared with control subjects, night eaters
had attenuation of the nocturnal rise in plasma melatonin and leptin levels
(P<.001 for both) and higher circadian levels
of plasma cortisol (P = .001).ConclusionA coherent pattern of behavioral and neuroendocrine characteristics
was found in subjects with NES.

https://jamanetwork.com/journals/jama/articlepdf/191250/jpc90030.pdf

Behavioral and neuroendocrine characteristics of the night-eating syndrome.

Objective

To compare the characteristics of obese persons with the night eating syndrome (NES) with those of nonobese persons with the NES.



Methods

Eighty subjects (40 with a body mass index [BMI] greater than 30 and 40 with a BMI less than 25) identified themselves on a website for the Night Eating Questionnaire (NEQ) as suffering from the NES. The responses of the 40 obese website subjects were compared with 21 obese persons with the NES who had undergone face-to-face interviews. The responses on the NEQ of the 40 obese and the 40 non-obese website subjects were then compared.



Results

There was no difference in the NEQ results of the 40 website obese subjects and 21 obese night eaters who had undergone face-to-face interviews. The responses of these same 40 obese subjects showed very little difference compared with those of the 40 nonobese subjects. The major difference between the two groups was the considerable younger age of the normal-weight NES subjects.



Discussion

The striking similarity in the characteristics between obese and nonobese subjects with the NES indicates that this disorder, considered until now to occur primarily among obese persons, also occurs among nonobese persons. The younger age of the nonobese subjects suggests that the NES may contribute to the development of obesity. © 2004 by Wiley Periodicals, Inc. Int J Eat Disord 35: 217–222, 2004.

Night eating syndrome among nonobese persons

Objective. The immune characterization of ulcerative colitis (UC) has been unclear and controversial. One possible explanation for the discrepancies between earlier cytokine studies in UC may be the fact that the patients included were on immunosuppressive therapy. Thus, the aim of this study was to determine the tumor necrosis factor-alpha (TNF-α) level and TH1/TH2 cytokine expression (mRNA) profile in patients with untreated UC. Material and methods. Forty-four untreated UC patients, 10 untreated Crohn's disease (CD) patients and 28 healthy controls were included in the study. Colon biopsies were processed for quantitative measurements of TNF-α, interleukin (IL)-10, IL-18, IL-4 and interferon-gamma (IFN-γ) mRNA using real-time polymerase chain reaction (PCR). TNF-α expression in T-cell lymphocytes (CD3) and macrophages (CD68) were further characterized by immunohistochemistry (IHC). Results. Compared with the level in normal controls, the TNF-α mRNA level in UC patients was clearly increased, especially...

Tissue levels of tumor necrosis factor-alpha correlates with grade of inflammation in untreated ulcerative colitis

Background: Fiber supplements added to a caloric diet have additional effects on weight reduction in overweight subjects. The aim of this study was to compare the effect of various commercial fiber supplements (glucomannan, guar gum and alginate) on weight reduction in healthy overweight subjects. 

Material/methods: One hundred and seventy six men and women were included to receive either active fiber substance or placebo in randomized placebo-controlled studies. The fiber supplements consisted of the viscous fibers glucomannan (Chrombalance), glucomannan and guar gum (Appe-Trim) and glucomannan, guar gum and alginat (Glucosahl). 

Results: All fiber supplements plus a balanced 1200 kcal diet induced significantly weight reduction more than placebo and diet alone, during a five week observation period. However, there were no significant differences between the different fibers in their ability to induce weight reduction, which was approximately 0.8 kg/week (3.8 +/- 0.9, 4.4 +/- 2.0, 4.1 +/- 0.6 in the Chrombalance, Appe-Trim and Glucosahl group, respectively). 

Conclusions: Glucomannan induced body weight reduction in healthy overweight subjects, whereas the addition of guar gum and alginate did not seem to cause additional loss of weight.

Experiences with three different fiber supplements in weight reduction.

A weight-reducing potential has been ascribed to high dietary fibre intake. To investigate the practical reliability of this hypothesis, fifty-three moderately overweight females (BMI > 27.5 kg/m2) on reduced energy intake (1200 kcal/day) were treated for 24 weeks with a fibre supplement on a randomly, double-blind, placebo-controlled basis. The fibre was administered as an initial dose of 6 g and a maintenance dose of 4 g. Body weight and blood pressure were recorded weekly during the first 3 months and thereafter every second week. Blood samples were drawn at start and at end of the study. Initial body weights were 75.6 +/- 1.6 kg in the fibre group versus 75.5 +/- 1.6 kg in the placebo group. After treatment, mean weight loss in the fibre group was 8.0 kg versus 5.8 kg in the placebo group (p < 0.05). Systolic and diastolic blood pressures were significantly reduced in both groups without differences between the groups. Serum concentrations of cholesterol, triglycerides and uric acid were significantly reduced in the group with reduced energy intake, whereas no additional effect was observed when fibre was supplemented. Serum concentrations of potassium and sodium did not change significantly. The results suggest that a dietary fibre supplement in combination with a hypocaloric diet is of value as an adjunct in the management of overweight.

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Grethe Støa Birketvedt

Papers

Behavioral and neuroendocrine characteristics of the night-eating syndrome.

Night eating syndrome among nonobese persons

Tissue levels of tumor necrosis factor-alpha correlates with grade of inflammation in untreated ulcerative colitis

Experiences with three different fiber supplements in weight reduction.

Long-term effect of fibre supplement and reduced energy intake on body weight and blood lipids in overweight subjects.