M. A. van Baak

How much physical activity is enough to prevent unhealthy weight gain? Outcome of the IASO 1st Stock Conference and consensus statement

A consensus meeting was held in Bangkok, 21–23 May 2002, where experts and young scientists in the field of physical activity, energy expenditure and body‐weight regulation discussed the different aspects of physical activity in relation to the emerging problem of obesity worldwide. The following consensus statement was accepted unanimously.

The Diet, Obesity and Genes (Diogenes) Dietary Study in eight European countries – a comprehensive design for long-term intervention

Diogenes is a Pan‐European, randomized, controlled dietary intervention study investigating the effects of dietary protein and glycaemic index on weight (re)gain, metabolic and cardiovascular risk factors in obese and overweight families in eight European centres. The article is methodological in character, and the presentation of ‘results’ will be limited to baseline characteristics of the study populations included. A total of 891 families with at least one overweight/obese parent underwent screening. The parents started an initial 8‐week low‐calorie diet and families with minimum one parent attaining a weight loss of ≥8%, were randomized to one of five energy ad libitum, low‐fat (25–30 E%) diets for 6 or 12 months: low protein/low glycaemic index, low protein/high glycaemic index, high protein/low glycaemic index, high protein/high glycaemic index or control (national dietary guidelines). At two centres the families were provided dietary instruction plus free foods for 6 months followed by 6‐month dietary instruction only. At the remaining six centres the families received dietary instruction only for 6 months. The median weight loss during the low‐calorie diet was 10.3 kg (inter‐quartile range: 8.7–12.8 kg, n = 775). A total of 773 adults and 784 children were randomized to the 6‐month weight (re)gain prevention phase. Despite major cultural and dietary regional differences in Europe, interventions addressing effects of dietary factors are feasible with a reasonable attrition.

Prevalence of overweight and obesity in the Netherlands.

This paper shows the trends in the prevalence of overweight (body mass index [BMI] ≥ 25 kg m−2) and obesity (BMI ≥ 30 kg m−2) in the Netherlands. Overweight (obesity) prevalence in adult males increased from 37% (4%) in 1981 to 51% (10%) in 2004, and in adult females from 30% (6%) in 1981 to 42% (12%) in 2004, according to self‐reported data. In boys and girls, obesity prevalence doubled or even tripled from 1980 to 1997, and again from 1997 to 2002–2004 a two‐ or threefold increase was seen for almost all ages. According to the most recent data, overweight (obesity) prevalence figures range, depending on age, from 9.2% to 17.3% (2.5–4.3%) in boys, and from 14.6% to 24.6% (2.3–6.5%) in girls. There is a lack of data on the national prevalence of overweight and obesity based on measured height and weight and on prevalences in different subgroups of the population. Regular national representative health examination surveys that measure height and weight are needed to assess the prevalence of overweight and obesity and its distribution over subgroups in the population, and to properly direct and evaluate prevention activities.

Possible involvement of the adipose tissue renin-angiotensin system in the pathophysiology of obesity and obesity-related disorders

Angiotensin II (Ang II), acting on the AT1 and AT2 receptors in mammalian cells, is the vasoactive component of the renin‐angiotensin system (RAS). Several components of the RAS have been demonstrated in different tissues, including adipose tissue. Although the effects of Ang II on metabolism have not been studied widely, it is intriguing to assume that components of the RAS produced by adipocytes may play an autocrine, a paracrine and/or an endocrine role in the pathophysiology of obesity and provide a potential pathway through which obesity leads to hypertension and type 2 diabetes mellitus. In the first part of this review, we will describe the production of Ang II, the different receptors through which Ang II exerts its effects and summarize the concomitant intracellular signalling cascades. Thereafter, potential Ang II‐induced mechanisms, which may be associated with obesity and obesity‐related disorders, will be considered. Finally, we will focus on the different pharmaceutical agents that interfere with the RAS and highlight the possible implications of these drugs in the treatment of obesity‐related disorders.

Daily physical activity of schoolchildren with spastic diplegia and of healthy control subjects

OBJECTIVE To assess the differences in daily physical activity between children with spastic diplegia and healthy schoolchildren, to determine whether special physical activity programs are needed in the population with cerebral palsy. DESIGN Cross-sectional design. SETTING Childrens rehabilitation center Franciscusoord (day care center) and elementary schools. SUBJECTS Children with spastic diplegia (5 boys; mean (+/- SD) age 8.0 +/- 1.4 years; 9 ambulant, 1 wheelchair use) and healthy children (5 boys; mean (+/- SD) age 8.4 +/- 1.0 years). MEASUREMENTS Total daily energy expenditure (TEE) and sleeping metabolic rate (SMR) were measured by the doubly labeled water technique and a respiration chamber. The TEE/SMR ratio was used as an index for the level of daily physical activity. RESULTS The TEE/SMR ratio under normal daily conditions in the children with cerebral palsy (mean +/- SD): 1.56 +/- 0.19) was significantly lower (p < 0.05) than in their healthy peers (mean +/- SD: 1.83 +/- 0.23) and was similar to the TEE/SMR ratio in a room-sized chamber. CONCLUSION Children with spastic diplegia are considerably less active than their healthy peers. We recommend special physical activity programs for these children.

The effect of a low-fat, high-protein or high-carbohydrate ad libitum diet on weight loss maintenance and metabolic risk factors.

Background:High-protein (HP) diets are often advocated for weight reduction and weight loss maintenance.Objective:The aim was to compare the effect of low-fat, high-carbohydrate (HC) and low-fat, HP ad libitum diets on weight maintenance after weight loss induced by a very low-calorie diet, and on metabolic and cardiovascular risk factors in healthy obese subjects.Design:Forty-eight subjects completed the study that consisted of an energy restriction period of 5–6 weeks followed by a weight maintenance period of 12 weeks. During weight maintenance subjects received maltodextrin (HC group) or protein (HP group) (casein (HPC subgroup) or whey (HPW subgroup)) supplements (2 × 25 g per day), respectively and consumed a low-fat diet.Results:Subjects in the HP diet group showed significantly better weight maintenance after weight loss (2.3 kg difference, P=0.04) and fat mass reduction (2.2 kg difference, P=0.02) than subjects in the HC group. Triglyceride (0.6 mM difference, P=0.01) and glucagon (9.6 pg ml−1 difference, P=0.02) concentrations increased more in the HC diet group, while glucose (0.3 mM difference, P=0.02) concentration increased more in the HP diet group. Changes in total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, insulin, HOMAir index, HbA1c, leptin and adiponectin concentrations did not differ between the diets. No differences were found between the casein- or whey-supplemented HP groups.Conclusions:These results show that low-fat, high-casein or whey protein weight maintenance diets are more effective for weight control than low-fat, HC diets and do not adversely affect metabolic and cardiovascular risk factors in weight-reduced moderately obese subjects without metabolic or cardiovascular complications.

The peripheral sympathetic nervous system in human obesity

The peripheral sympathetic nervous system is a key factor in the regulation of energy balance in humans. Differences in sympathetic nervous system activity may contribute to variations in 24 h energy expenditure between individuals. β‐Adrenoceptors play a more important role than α‐adrenoceptors in this regulation. The involvement of both β1‐and β2‐adrenoceptor subtypes has been demonstrated, the role of the β3‐adrenoceptor subtype is not yet clear. Normal or increased levels of sympathetic nervous system activity and reduced reactivity appear to be present in established obesity. Furthermore, the sensitivity for β‐adrenoceptor stimulation is impaired in obesity. The blunted reactivity and sensitivity may contribute to the maintenance of the obese state. There are data to suggest that they may also play a role in the aetiology of obesity, because the impairments often remain after weight reduction. Furthermore, a negative correlation between baseline sympathetic nervous system activity and weight gain during follow‐up has been found in Pima Indians. Recently, genetic evidence about the involvement of adrenoceptors in obesity has become available. Although the results of association and linkage studies on polymorphisms in the β2‐, β3‐ and α2‐adrenoceptor genes are inconsistent, the functional correlates of some of these polymorphisms (changes in agonist‐promoted down‐regulation, protein expression levels, lipolytic sensitivity, basal metabolic rate, sympathetic nervous system activity) suggest that they may be important in the aetiology of obesity.

Regulation of average 24h human plasma leptin level; the influence of exercise and physiological changes in energy balance.

OBJECTIVE: The effects of short-term moderate physiological changes in energy flux and energy balance, by exercise and over- or underfeeding, on a 24 h plasma leptin profile, were investigated.DESIGN: Subjects were studied over 24 h in four randomized conditions: no exercise\energy balance (energy intake (EI)=;energy expenditure (EE)=;11.8±0.8 MJ); exercise\energy balance (EI=;EE=;15.1±0.6 MJ); exercise\negative energy balance (EI=;11.8±0.8 MJ, EE=;15.1±0.8 MJ); exercise\positive energy balance (EI=;18.6±0.7 MJ, EE=;15.1±0.6 MJ).SUBJECTS: Eight healthy, lean men (age: 23.5±7.0 y, body fat 14.1±5.4%, body mass index (BMI): 21.4±2.3 kg\m2).MEASUREMENTS: Blood was sampled every hour during the daytime (09.00–23.00 h) and every two hours during the night (01.00–09.00 h) for analysis of plasma leptin, insulin, glucose, FFA and catecholamines.RESULTS: Plasma leptin levels were highest around 01.00 h (mean±s.e.m. 4.9±2.0 ng\ml) and lowest around 11.00 h. (2.3±0.7 ng\ml). An increased 24 h EE, induced by exercise under conditions of energy balance, significantly decreased the peak and average 24 h plasma leptin concentration. A positive energy balance, by overfeeding, resulted in a significantly higher amplitude of the 24 h plasma leptin curve, compared to a condition of energy balance.CONCLUSION: Exercise decreases peak and average 24 h plasma leptin concentration and a moderately positive energy balance increases the amplitude of the 24 h plasma leptin profile. These effects are not acute, but are manifest within 24 h. The variations of average 24 h FFA and average 24 h glucose concentrations almost fully explained the variation in average 24 h leptin concentration across trials.

Physical training of school children with spastic cerebral palsy: effects on daily activity, fat mass and fitness.

Effects of two 9-month sports programmes (four or two sessions per week) on level of daily physical activity (PA), fat mass (FM), and physical fitness were assessed in children with spastic cerebral palsy (CP; n = 20, 9.2 +/- 1.4 yr), randomly assigned to an experimental and control group after matching. Four sessions per week tended to increase PA ratio (24-h energy expenditure/sleeping (resting) energy expenditure) after 9 months from 1.34 +/- 0.25 to 1.55 +/- 0.18 (P = 0.07; not different versus controls). FM increased continuously in the control group (after 9 months + 1.1 +/- 1.6 kg, P < 0.05), whereas the experimental groups showed no changes. Training (respectively four and two sessions) increased peak aerobic power 35% (P < 0.01; P < 0.05 versus controls) and 21% (P < 0.01; P = 0.17 versus controls). Results also suggest that training has a favourable effect on isokinetic muscle strength. No training-related effects were found on anaerobic power. It was concluded that although aerobic training has a limited effect on PA in children with CP, it may prevent deterioration in body composition and muscle strength. Furthermore, training has a favourable effect on peak aerobic power.

Consumption of sugars and body weight

The role of dietary sugars in the current obesity epidemic is much debated and opposing views can be found in the lay as well as scientific literature. Here we have reviewed the recent scientific literature on consumption of sugars and body weight. Main focus was on three questions: (i) What is the evidence that intake of dietary sugars is associated with higher body weight than intake of non‐sugar carbohydrates? (ii) What is the evidence that sugars in liquid form are associated with higher body weight than sugars in solid form? (iii) What is the evidence that diets with a low glycaemic index (GI) or glycaemic load (GL) are associated with lower body weight than diets high in GI or GL? We conclude that (i) there is insufficient evidence that an exchange of sugar for non‐sugar carbohydrates in the context of a reduced‐fat ad libitum diet or energy‐restricted diet results in lower body weights; (ii) observational studies suggest a possible relationship between consumption of sugar‐sweetened beverages and body weight, but there is currently insufficient supporting evidence from randomized controlled trials of sufficient size and duration; (iii) at this moment there is insufficient evidence to support a difference between liquid and solid sugar intake in body‐weight control and (iv) there is some, although not consistent, evidence for a lower body weight on diets with a lower GL, but the effect is likely to be small. There is currently no convincing evidence for a role of GI independent of GL.