Diet is undoubtedly one of the most crucial components of our lifestyle in terms of impact on our health. With the wealth of information and culinary options available to us, it is unsurprising that there is much debate regarding what is meant by a ‘healthy diet’.

The importance of meal frequency for weight loss

Whether favouring intermittent fasting or advocating the importance of small but regular meals, meal frequency is often implicated as being a crucial element of maintaining a healthy diet.

Fasting is not a new concept, being prevalent in multiple religions and historically seen as a display of discipline and willpower by many cultures. For example, the Sanskrit word ‘vrata’, literally meaning ‘devotion’, refers to a religious observance in Hinduism typically associated with abstinence from food. In a modern society of plenty, fasting can extend past religion, with intermittent fasting rapidly becoming a popular weight loss method.

“Healthy snacking habits can even help to promote a decrease in waist circumference and BMI.”

Restrictive eating periods provide an effective way to control energy intake, leading to reduction of multiple parameters such as BMI, waist circumference and body weight. Whilst these effects are often only short term, for example if poor eating habits are reinstated, in many cases they can lead to long weight management and health benefits. There is also evidence that fasting can produce reductions in serum glucose and IGF-1 (insulin-like growth factor, a protein similar to the hormone insulin). Glucose and IGF1 have been implicated in pro-ageing and cancerous signalling pathways, and therefore fasting could provide some protection against such harmful effects.

Furthermore, it has been proposed that fasting can be beneficial for brain function. During the fasting state, glycogen reserves in the liver are utilised as a source of glucose until they are depleted. Then, fatty acids are converted into ketone bodies, which may be utilised by specific tissues in the body such as cardiac muscle or the brain, which can meet up to 50% of its energy requirements using ketone bodies. The ketone body β-hydroxybutyrate can induce the expression of brain-derived neurotrophic factor, promoting synaptic plasticity and increasing the ability of cells to survive stress.

Equally, a greater number of smaller meals is promoted by many, as more regular and frequent feeding patterns can help to increase satiety and decrease caloric intake during the next meal. Reflected by the high drop-out rates for many studies involving fasting, eating more regularly is like to be more sustainable. Healthy snacking habits can even help to promote a decrease in waist circumference and BMI.

A caloric deficit is all that is required for weight loss - there is evidence that this can be achieved by either fasting, or smaller meals throughout the day. In terms of importance, quantity and quality of food far surpass frequency of feeding.

Consumption of dairy products should be avoided

Dairy alternatives such as soy, oat and almond are soaring in popularity. As well as concerns regarding the ethical integrity of the dairy industry, many are worried about the effects of dairy on their health. In those who are lactose intolerant, eating dairy typically leads to unpleasant symptoms such as stomach cramps and diarrhoea. This is likely due to a lack of the enzyme required to digest a particular sugar in milk (lactose). A substantial 65% of the global population is estimated to show some extent of lactose intolerance after childhood.

“Optimal nourishment is likely to vary considerably between person to person.”

However, in those who can consume dairy without any ill effects, there are notable health benefits associated with dairy intake. Dairy products tend to be protein rich, promoting satiety, and are an excellent source of ‘essential amino acids’ - amino acids that cannot be synthesised by the body and therefore must be obtained from dietary sources. There is also evidence that dairy can help to manage blood glucose levels. The whey protein fraction contains certain branched chain amino acids, notably leucine, which can help to promote the release of GIP, a polypeptide that enhances insulin release, promoting uptake of glucose from the blood.

It is well known that dairy is a good source of calcium, helping to protect against osteoporosis (a bone weakness disorder) later in life. Whilst dairy alternatives can be fortified with calcium, the calcium may not be absorbed as effectively from dairy alternatives.

Overall, abstaining from dairy can help to lower calorie intake, it is not necessarily a dietary modification required to promote a healthy lifestyle.

The anabolic window hypothesis

Many popular fitness influencers emphasise the importance of consuming a ‘post-workout’ source of nutrition, usually a protein shake, within a short time after completing an exercise routine. It has been suggested by many in the fitness community that high quality nutrition within this ‘window of opportunity’ will replenish energy reserves in a specific way that maximises exercise performance and body composition, in terms of hypertrophic muscle gain. Currently, there is insufficient evidence available to support this theory. Whilst maintaining an adequate caloric and protein intake is essential to maintain or build muscle mass, there does not appear to be a time restrictive component for optimal recovery.

The degree of flexibility enjoyed by humans in terms of feeding has introduced a new level of complexity. The evolutionary concern of whether or not food will be available is gradually being replaced with decisions regarding what and when we should eat. There are many general components of a healthy diet, such as meeting recommended daily amounts for particular vitamins. However, evidence for the benefits of other feeding behaviours is more tenuous - optimal nourishment is likely to vary considerably between person to person.