Dietary carbohydrate manipulation and energy balance (v1)
Research type
Research Study
Full title
The effect of dietary carbohydrate manipulation on all major aspects of energy balance: A 12-week randomised controlled trial
IRAS ID
227478
Contact name
Aaron Hengist
Contact email
Sponsor organisation
University of Bath
Clinicaltrials.gov Identifier
Duration of Study in the UK
3 years, 0 months, 30 days
Research summary
Summary of Research
Sugar is perceived negatively, leading to government taxation and targets to reduce consumption. These actions have been taken based on the limited evidence that high-sugar diets are associated with greater total energy intake. However, energy intake is only one half of the energy balance equation (energy in vs energy out). Without considering energy expenditure, it is impossible to fully understand the effects of sugar on health. Removing dietary sugar or carbohydrates from the diet may influence energy balance through mechanisms other than energy intake – for example by reducing levels of physical activity. \n\nUnderstanding dietary regulators of energy balance is more important than ever because diseases like obesity are a consequence of energy surplus (i.e. energy in > energy out). No studies have investigated a causal role of dietary sugar or carbohydrate on energy balance. The proposed research will seek to understand the responses to manipulating dietary carbohydrate and sugar content on energy balance and health. This research will enable the public to make informed dietary choices about carbohydrate and sugar consumption. \n\nTo achieve this, healthy non-obese adults, aged 18-65 years will be recruited to take part in an intervention study with measures of energy intake, energy expenditure, metabolic health, gut microbiota, and appetite. All laboratory trials will take place at the University of Bath. Participants will be randomised to consume one of three diets for a period of 12 weeks, with laboratory visits at baseline, at week 4, and at week 12:\n\n1.\tCONTROL (Moderate sugar) – reflecting the composition of a typical European diet\n\n2.\tLow sugar – the same composition of a typical European diet but with <5% energy intake from sugar\n\n3.\tLow carbohydrate – low carbohydrate diet with <5% energy intake from sugar, replacing carbohydrate energy with fat \n
Summary of Results
Restriction of dietary free sugars to less than 5% of energy intake, or overall carbohydrate to less than 8% of energy intake, does not cause a detectable change in physical activity energy expenditure across 4 weeks or 12 weeks. Prolonged adherence to either intervention does, however, result in a reduction in energy intake which, in the absence of changes in resting metabolic rate, diet induced thermogenesis, and physical activity, result in a reduction of fat mass.
Restriction of free sugars also results in a reduction in LDL-cholesterol concentrations without altering glycaemic responses, which provides support for government guidelines advocating restriction of free sugars to less than 5% of energy intake.
Ketogenic carbohydrate restriction reduced metabolic flexibility and glucose tolerance, and increased LDL-cholesterol and Apolipoprotein B concentrations, suggesting the reductions in fat mass do not provide additional benefits to metabolic health in otherwise healthy humans.
For individuals who are generally healthy, these data support restricting free sugar intake and do not support adoption of low-carbohydrate ketogenic diets.
REC name
South West - Central Bristol Research Ethics Committee
REC reference
18/SW/0178
Date of REC Opinion
17 Oct 2018
REC opinion
Further Information Favourable Opinion